The Contours (Roam, GPS, and +) have a slide- you push it forward and it is recording, you push it back and the recording stops (it also beeps once when recording and twice when you stop). It's very simple and you immediately know whether you are recording or not. The Countours also have the ability to take photographs at intervals.
The one downside to the Contour Roam is that it will only record at 30 frames per second, while the GPS and + will record at 60 frames per second at 720p.
One other cool thing with the GPS and the + is that you can use an Android or iPhone as an LCD and to control it using bluetooth.
Originally Posted by Vitamin Ski
Well, the GoPro beeps once when it records, and beeps three times when it is done recording a clip.
If it is windy or loud, you'd have to take it off and see the red indicator light flashing, which means it is recording.
The GoPro also has the ability to take photographs at intervals, eliminating the need for a camera (which is nice for compulsive photographers like me)