"Check Your Guns At the Door"
I usually have a "check your guns at the door" policy in any meetings where the attention of participants is required. This means that all cell phones, pagers, laptops, etc. have to be turned off.
To make it easier for people to do without their gadgets, and harder for them to come up with excuses, I send a preprinted agenda with space for people to take notes on. (People who take notes on their laptops are generally also checking their e-mail several times an hour, checking the news and their stocks, or possibly even playing games! The tempatation of all that information and entertainment at your fingertips is simply too great.)
This makes our meetings much more productive, and the level of participation much higher. (Maybe partly because everybody is in a hurry to conclude our business and get back to their e-mail!)