Using Cel Phone Chess Clocks in Tournaments

Hey all, looking for input.  Starting a high school chess league, and it will be rated using our own rating system (not USCF rated).  Hardly any chess clocks owned in the area, so we're going to allow cel phone chess clock apps.  Figure the chance of cheating is slim, since both sides can see the clock.  Still, what kind of cheating prevention measures should we take, if any?

Ideas we've had include  

• Allow floor judges to inspect the phone before, and after, a game  
• Randomly specify whose clock gets to be used, before each round (White, or Black)  
• Have a random pattern of trading clocks between boards (i.e. for Round 1, announce at start of round that Board 1 trades clock/phone with Board 2, etc)  
• Keep cel phone usage forbidden for any other purpose in the playing hall

Thoughts?  Anyone else hold tournaments with cel phone chess clock apps, how didi it go?  Any issues arise?

It sounds workable to me from a cheas point of view. Because it's not a USCF rated tournament. Your rating system, your rules. It's not ideal from a privacy or a hygiene point of view. People use their smartphones all the time and they can get quite mucky.

The hygeine issue is the easier one to solve put out alcohol wipes or insist that phone screens be cleaned in some other way.

The second issue is more tricky: privacy. Phones need to ne unlocked and on the table netween two kids who may have a longstanding beef, or even a bullying relationship. It would be far too easy to grab the phone and look through it at messages or photos. That possibility will put off some players. There is also the risk of someone deliberately hitting the clock too hard or knocking the phone across the room. Now you are potentially liable for the cost of a new smartphone.

Overall then, in a school setting, it is not a good idea on a large scale, with real world children in my opinion.