Hi,
Found this neat gadget. It is a remote control pager, originally intended for the elderly and bed ridden to summon assistance. It can also be used to bring a child back to task or help them snap out of a daydream. I originally dreamed of something like this myself to help my son at Soccor, he is goalie and there is a lot of distraction time! He no longer likes me standing at the net hollering “GET READY! HERE THEY COME!” I thought it would be nice to have a descrete remote control device to get his attention. (I was originally thinking of a mild zap, bad me! But I think I’ll try vibration before electricution, LOL!) It is also something teachers can use in the classroom. It has a chime and a vibration as well. I have seen it go from $39 to $99. So shop around.
http://www.dynamic-living.com/personal_pager.htm