Is there any doubt as to the importance of cell phones (called mobile phones here in Australia) to the average human being? I can safely say that now as more than half of the world population is able to at least own a phone. For the record, there are more mobile phones here in Australia than there are residents of Australia. That means some of us have more than one!
In times past, seeing a person walking down the street mumbling to themselves was a sure sign of madness or insanity. Today, it means they have Bluetooth(tm) enabled. Have you ever had your cell phone ring during a performance? I put mine on silent ring but lately I've simply left it off stage. You see, I have one of those strong magnetic catches on the cover which grabs my stage props at the worst possible time. There's nothing worse than seeing a photo of yourself with one of your linking coat hangers dangling mysteriously from your belt area. Fortunately, I caught that during my video taped rehearsal and stopped wearing my phone ever after while on stage.
It does give me an idea for close up, though. How about you? can you imagine how easy it would be to hide out a magnetic item on that innocent looking phone on your belt? Think about it. Everyone seems to have a phone somewhere on their person these days. Why not carry yours on your belt?
If you don't like that idea, here's another one that would put a magnet on your belt. Go here and look at the variety of rare earth magnets available. http://www.kjmagnetics.com/ Buy a small, thin one and glue it to your belt. Cover it with some vinyl tape of the proper size & color and you have the miraculous magnetic holder of your dreams. Even if you don't wear a belt, you can open the cloth along the beltline from inside the waist and insert a magnet there. Women often don't wear belts and this is a good way to create a very innocent means to deliver something magnetic into your hand.
Fold a note with a memorized serial number into a paper clip and put it there. Exchange it at your leisure with a borrowed bill of the same denomination. A recent post on the alt.magic newsgroup offered magnetic cards for sale. Aside from the normal questioning of the seller's having made them "professionally" or not, the cards could be used as a force card, placed in an envelope and fairly mixed with other cards which are also placed in envelopes. The act of bringing them near to the hidden magnet one by one will allow you to find that card no matter how fairly they are mixed.
So, use that noggin of yours and come up with ways to use this easily hidden device.