The Speedpuck is really simple. It has three modes you toggle between with the button: speed, max speed and compass. In addition, visible in all the modes there is a angle shift detector that's really slick, showing you when you hit a wind shift. Like a tactical compass but without the calculation in your head.

Demo:



I have three velocitek devices, each can do different things. The SC-1 is the most complex, it adds distance to the line, VMG, and more with two displays so you can see two bits of info at once.