As far as I know, this is the cheapest reverse geocaching box ever made. If you bought all the parts it would be about $16, excluding the phone required for use. In theory, that price could be dropped even further, but I lack the knowledge in order to communicate with a TI launchpad using a 3.5mm cable and had to opt for bluetooth instead. I will be using it in a day or two to ask a girl to prom.
Components
1×
TI Launchpad
MSP-EXP430G2
1×
HC-06 Bluetooth Module
Almost any serial bluetooth module should work, this is just the one I picked.
3×
2N2222 NPN transistor
Again, the exact part used here is somewhat trivial, this is just what I had on hand.
1×
Double Throw Double Position Latching Relay
Preferably 3 volt activation, although I'm using a 5 volt relay.
1×
Relay
Preferably 3 volt activation, although I'm using a 5 volt relay.
I have to ask her today! I've been working on the project non stop, and I'll be posting a full write up soon! I made the decision to swap to an arduino, and yes, I know, it's an arduino *shudders* but... it had to be done fast, and arduinos are a proven, working method, that managed to pull me through on this one. Besides, It's not like I'm just blinking an LED or something ;) Anyways, thanks for all of you who have taken a look at this, and I'll probably be posting a revised version that's cheaper after my initial full write up. We'll see if she says yes!
Up until this point, I've been working on it independent of hackaday projects. I have the whole thing planned out, the enclosure painted, and I hope to finish soldering the circuit tonight. Once I'm done I plan on posting a build-log.