ORIGINAL: cjg
Turning off transmitters while operating r/c is a very bad thing. It can cause havoc with controls. That is why all the manuals on anything r/c tell you the rule radio on first and off last, all the time.
I bought a drop module for my SC but haven't tried it yet.
Later...tried the module. Wouldn't work on the ground, but when it was airborne it released if you hold the button down for a second. It does cut the motor so make sure you are on an appropriate glide path. I mounted it with the magnet forward so that wind tends to pull it open.