Adventures with mobile phones

At this years O2C Doeberl Cup we tried a new system of dealing with the issue of mobile phones. As the FIDE rules currently stand, no player can have a mobile phone on their person during a competition game of chess, and if they do, the punishment is an automatic loss.
The problem with this rule is of course in its enforcement. On the one hand there is no practical way of detecting mobile phones, part from when they give themselves away, but on the other, I am sure plenty of players do carry them during games. And if we enforced the rules as they are written I suspect that there would be around 20 disqualifications per round.
So for this years event, we provided a storage system for phones. The organisers purchased a large number of zip lock sandwich bags, and asked the players to leave their phones at the results desk. On each bag was written the name of the owner, and then all the phones were stored in boxes at the desk.
In practice there were about 50 phones handed in at the start of each round, and overall the system worked well. Of course it was helped by the team working the results desk, as they handled this extra task with the professionalism that they handle all their other duties.
During the operation of this system, we had one phone in storage go off, although it was set to vibrate. We did not penalise the player concerned, as this was exactly the situation the system was deigned to deal with. (Note: We did ask the players to switch their phones of before handing them in). We did have one phone forfeit during the tournament however, so clearly not everyone took advantage of the situation. It also helped in one specific case where a player was in the habit of taking their bag with them whenever they left the playing hall, even when their game was still in progress. Having told the player not to do this (either leave the bag outside, or at the table), the player argued that possession of the bag was necessary.However the player then surrendered the phone, avoiding an unnecessary level of suspicion.
As for the security of the phones, every single one was returned to the owners, and their were no complaints about the system.