you cannot prevent computer cheating by any means. There are hand held devices that can play at 2400+ There are people at tournaments who "just want to enter their moves" on a pda or what ever and have a 2500 program running.
USCF Rated Play on ICC and Chess.com

you cannot prevent computer cheating by any means. There are hand held devices that can play at 2400+ There are people at tournaments who "just want to enter their moves" on a pda or what ever and have a 2500 program running.
Why would any tournament director allow having a tablet or computer on boars during a game? certainly I have not seen that being allowed
http://monroi.com/products/personal-chess-manager.html
Bad idea, engine users would be running all over the place.