How to make a remote controlled air horn from an android phone?
Okay so my problem is as follows: my friend always needs a ride every week to dance so on my way I swing by and pick him up. However he likes to take naps and is an incredibly deep sleeper so I thought it would be funny to install a remote controlled air horn to wake him up and relieve some of the irritation I get from him not being ready.
So my question is what would be the best way to go about this?
I have so far considered Bluetooth and even an arduino with a webserver but I kind of want to keep it as cheap as I can because its just to play a simple prank. So any ideas on how to go about this would be great.