The party, where I want to wear the vest, takes place in 8 days. That’s a very – ahm – condensed timeframe to advance the project from an idea into a working state.

I wouldn’t necessarily consider this a problem. I need a clear deadline and some sort of pressure to do stuff and work best. So that’s a given.

I also need a good plan and milestones, so I don’t get lost in unimportant details and I need to cut corners wherever possible (not that iPhones have that many corners to begin with, most of them are rounded) to progress as fast as possible. I don’t need perfect solutions for the first working vest – I need working ones.

So, what's the bare minimum?

• 4 Phones in portrait mode side-by-side on the front and the back of the vest. Each displaying a random number for some time
• 8 Phones on either side, maybe 4 more (two left and right) on/as straps leading to the shoulders.
• That would be 12 phones on the front and back, so 24 in total. Do I have that many phones? I am pretty sure (yet I still must get them from the office as I am on holiday right now)
• Would that all be the same phone model as initially planned? Not quite sure, maybe not.
• Does that matter? – not really. I plan to 3d-Print mounting for each phone, so as long as the screens are roughly the same size it should be fine.
• I will use a web browser and some JavaScript to display the digit. Stored locally, so no internet/Wi-Fi connection is required.

Ok, the 4-phone on either side version sounds more like a fallback solution that can be achieved using some glue, tape and a safety vest. Good to have that.

What do I really want to have?

Do I have bigger plans and ideas that would require a network or even internet connection? Definitely! But let's not go overboard with ideas and settle for a minimum first.

Nevertheless, I will write down additional cool stuff I have in mind:

• Have the digits scroll through the phones
• Implement some sort of voice recognition, so that every time a phone picks up someone saying a number, all the phones are displaying it - that would be really awesome, but will most likely require an internet connection to offload voice recognition. It would definitely require the devices to be interconnected via Wi-Fi. Not that much of a problem
• Send the video of a front-facing phone’s camera to the opposing one on the backside and vice versa to sort of create the illusion of a “hole” in my body
• Display audio activated Winamp-Style visualizations. Would be cool for further use on concerts and festivals, but not all that useful at the party – I plan to stick with the numbers theme

Creating the possibility that the phones are somehow synchronized (I think of WebSockets) will allow me to quickly integrate new devices. The party will start outdoors, but it will transition the birthday person’s home later on. Other guests could then simply open a website and place their phone somewhere around the apartment, so when the (planned) number recognition kicks in the corresponding number is literally (or should I say digitally) displayed everywhere.

I am kind of having an epiphany right not. I simply want to write a wordplay on digits vs letters and realized, why its called digital. Digits! As opposed to literals – letters. Mind blown. But back to the topic.

Challenges

Thinking about the project, what would be the biggest challenges to overcome?

Battery runtime

Even with the minimal glue-and-tape version battery runtime could be an issue. The party starts at 14:00 (so 2 pm freedom-time) and will likely go on until 5 in the morning or so next day. That being an ambiguous plan by itself (even without the phones), considering that the screens need to be at maximum brightness while being outside, I doubt that the phones will last with one charge of their already aged batteries. So I need an easy and quick way to recharge them all at once or even have them connected to a power bank all the time. Considering the amperage needed to charge 24 phones simultaneously that’s not really an option. I could charge like 4 phones at a time and rotate charging, but that will also drain a powerbank rather quick. So my plan right now is to integrate charging-cables into the vest (maybe even make them part of the design) and take the vest off for an hour or so to let all the phones charge from mains power. Luckily I can borrow a 60 port mulicharger with 2.5 Amps on each port, so that’s sorted. And I can also keep a powerbank with me for the one or two phones with a particularly bad battery for re-charging on the go.

Hardware – Construction of the vest

So, basically, I considered two options on how to create the vest. Either mounting the phones to an existing vest (see minimal version) or create a vest consisting of iPhone “elements” and some straps and cables. The latter is my preferred option, so I settle on that.

My plan is to 3d-print a “tile” for each phone that’s integrating the charging port. All tiles are interconnected with straps or their charging cables, building the whole vest. Considering I will buy the cheapest charging cables available I don’t trust their mechanical stability, so I will go for the straps option. The part that’s going around the shoulders should be wide enough so that it's not uncomfortable to wear. On the sides I plan to integrate buckles, like on backpacks. 3D-Printable models are widely available, so that should be easy.

As for the phone’s cases, a lot of 3D-Printable models exist as well. I will have to slightly modify them in order to integrate a charging cable and mounting. Shouldn’t be that difficult, but I should start working on that early as it will require several iterations and printing stuff takes time.

Software

The software of the most basic version is easy. Just one html-file with some java-script displaying a randomly changing digit every 5 or so seconds. Store that locally on each phone and set it as stating-page of the browser.

Speaking of handling the phones: Maybe there is a freeware mobile-device management software out there making the whole process of changing settings and controlling the phones easier. I really wish the phones I have would be android phones. That would make the software-side a whole lot easier, but I have to work with what I got.

Further updates will (could?) include a WebSocket connection to a master-server (maybe a Raspberry Pi, I really would like to not be dependent on an internet connection) controlling the phones. The cherry on top would be, when I could be able to handle the whole voice-recognition-number displaying stuff locally. Considering the limited CPU and relatively high power consumption of a raspberry, I don’t think that’s an option. But I have to test that.

That’s it for now

So, that’s it for the moment, my next steps will be to get the phones and charging cables together with the multiport charger, to see what I have to work with. I thought of printing out phone-dummies for a first mock-up (well to be honest I already have a sheet of paper with 4 printed phones lying in front of me), but as I have to get hold and inventory the phones before Monday (when I have to work again) anyway – I want to make use of the available time during the weekend – I think the best next step would be to get the phones now and shop for the charging cables along the way.

Then I will have to craft a timeline for the whole project, so can stay on track and finish it until Thursday evening. Friday is for last-minute fixes, the party starts on Saturday. I will not have time for the vest on Saturday when I want so arrive on time.