Wireless datacenter environment monitoring

O

k.. Let's say my planning stages are complete. Not really.. but it's time to start building. My project involves wireles slave modules.. that talk to a master... that displays data on a webpage. So what am I going to start building first? The webpage!
Apparently if I want to use python to develop my interface the best option is to use Django 

No... not that Django... This Django: https://www.djangoproject.com/

I've been reading about it and.. well... me like it.

I'll try to build an interface with randomly generated data in the next days.

Wish me luck!

I just posted the video description for this prize entry. Here's the link!

The website will be programmed in python... why? Cause i've never used it before. I want to use this project to learn.

Anyways... thought I might write the web interface in python and save the data in a mysql database. There are probably better options... but I don't know them. I can always port to a better code if required. Let me know if you think tI should use something else... 

HTML5? I've no idea...

Haven't thought about power... I don't really want to use batteries because.. well.. 2or3 AA batts per module x 60 modules starts to get expensive/annoying battery-wise.

If the modules are going to be contained inside datacenter racks... then why no use USB power? They will only use a small amount of current (much less than the 500mA limit for USB) and USB ports will be wide available. External PSU jack can also be added.

 - "Security" might be a concern with USB-attached devices so the modules will only use the USB power lines. D+ D- won't be wired at all. This will isolate any "interference" between the arduino and the server/computer.

 - Humidity: HIH-4030

- Temperature: Thermistor inside a metal case?

 - Open/close doors: Reed switch + magnet?, Microswitch?, 

**NOTE: Could it be possible to add a gas detector to detect fire? Trigger an alarm maybe?

Central unit: 

 - Will be a raspberry pi. That's decided. No tech considerations given. I want to use a raspi. Period.

Modules:

 - Arduino of some sort. Needs to be small. Digispark maybe? Microudino? Any other options? 

 - In later stages of development may be changed to a custom board.

Options to transmitt data?

 - IR? Requires line of sight (kindoff..). One way only...

 - 433MHz modules? Need two per modules... RX and TX. Bulky.

 - NRF type transceivers? Two way communication. Small. 

 - Bluetooth? Never used it. Seems ... complicated.

 - Zigbee. Never used it. Don't like it's name.

Ok... I had the idea of what I wanted... I just couldn't visualize it. A few minutes googling images, some MSPaint (anyone know a nice simple linux alternative?) and now I can see it:

 - Each rack has a small arduino conencted to sensors and an RF link (NRF24L01?)

 - Central unit will be a raspberry pi. Why? Because I have never used one and this gives me a nice excuse.

 - RasPi will gather data via another rf link and present it on a custom website. A "heatmap" would be a nice addition. Not just plain sensor data numbers...