Dave Mitchell used a $10 device to release a camera shutter remotely. There is a discussion about this on the KAP forum. The device is a 433MHz transmitter and receiver pair with an advertised range of about 1000 feet. The receiver (photo above with Dave’s circuit in red) weighs only 5 grams and could fly on a kite or balloon rig with 4.5v of battery power to send a pulse to a Canon Powershot running CHDK.
This might be useful to those hoping to trigger two aerial cameras simultaneously, but who have no timer device. The signal from the receiver could be split into two USB cables to trigger two cameras at exactly the same time.
This might also be useful for triggering a single camera for mapping. Although mashing down the shutter button or using an intervalometer to shoot at regular intervals is handy and well tested, radio control has some advantages. With radio remote control, you can select the instant to shoot and avoid moments when the camera rig is swaying. By walking the kite or balloon to the next photo site, waiting for the rig to settle, and then triggering the shutter, far fewer photos need to be taken, and far fewer blurry, oblique, or duplicate photos must be sorted through after the flight.
I just ordered one of these. They take three or four weeks to arrive from China, so don’t delay!