The Standing Wave Amplitude Ratio (SWAR) increases by at least 6db because of the direct coupling with your body.
BTW: That's total BS - I just made that up
Your cell phone puts out 2 orders of magnitude more energy than your door locker/unlocker thinggy. I wouldn't worry about frying brain cells (unless you are in critical short supply of course).
I swear it works...My parking is gated...push button...nothing...push button...nothing...Hold to chin or head...push button...gate opens...all from the same distance.My wife even swears by it...that says alot LOL