A bit of feedback on this excellent idea.
I've been using one of these electronic stooge release's for a while now and I love it. I've had to include a microswitch to cut the current when the solenoid reaches the end of its travel. Had a spate of burnt-out solenoids that this simple cure seems to have fixed.
Also I use a 2S instead of 3S Lipo. This seems to give a less violent pull with still adequate power to release the model.
I fly alone most times, so I peg the thong to the ground. Also, when in front of the model, starting the engine, I restrain the model with a loop of rope around the tail pegged to the ground. Just in case of electronic malfunction or mechanical failure.
Steve