From the Dept. of “I Wonder What Will Happen If I Shove This Into There” Research comes news of handy substitute for a dedicated remote camera trigger.
Gurnarok’s test bed is rather limited, but other Web-published research suggests widespread applicability for any phone/game console/whatever headset with an inline on/off switch. You could even chop off the headphones and make it look considerably less cumbersome.
Feel free to do you own experiments and let us know what works.