For most Canon DSLRs on the market, you can use an infrared remote to start and stop video. There's been plenty of DIY remotes that attach to the handle of a shoulder rig, but if you're too lazy to tackle the project, Aputure now offers an inexpensive V-Remote. Switronix also offers a remote like this, but their price runs over $119 dollars (seen here).
To use the new Aputure V-Remote simply attach to the handle of your rig and flex the cable towards the infrared receiver (on front of camera). Pretty simple. You can find the new Aputure V-Remotes on eBay for a bit over $20 bucks (Click Here).
Aputure V-Remote Infrared Canon Start Stop Video Remote