Yeah somthing like these transmitter/receiver is great togheter with a gimbal I think.
Yes you will need a C3 cable to start & stop, C3 is a regular shutter release cord for almost all Canon DSLRs. I have four 603II so I use the three other ones where needed, and trigger the camera wireless from them.
The range is good don't know how long thought, and it starts the recording as fast as the buttons on the 5D3.