We do not have the official administering the throw-in start the clock. He uses his normal mechanics. Arm in the air, with the other arm counting. it's not difficult at all to have either or both of the other two officials hit the start button. But it should definitely be an off official. On FTs, there's no problem with any of the 3 officials starting it. The important thing is that it gets started.
Spaman, I do not believe DakTronics seels the system. The only place you can buy it is from Precision Time. I have linked their site below. Mike Constable, a former NBA official, developed the system.
http://www.precisiontime.com
Mark, to the contrary. The timer is required to continue to start and stop the clock as normal. Sometimes, it just doesn't work. About once per game, the clock will not stop on the whistle. There's usually a time or two that it won't start properly as well. It's up to the timer to make sure he follows normal procedure, so that no time is lost or gained.
We have 3 high schools locally that use it. I think it's use will continue to grow.