Trade Show Swipe card reader

I'm sorry if this is in the wrong place, please point me to the right one.

I've been tasked to find a reader for a magnetic stripe on a credit style card. Now this is not a credit card, this is an ID card handed out to attendees at trade-shows. The Attendee will have this card, go from booth to booth and swipe the card. There are PC devices out there to read them but here's the rub.

We'd like to take the card, swipe it on a Droid device, phone, tablet, etc. We imagine a swipe thingee attached to the phone, tablet, whathaveyou.

Any ideas how to go about looking for this? Everything we find is credit card centric and we do NOT need that. Thanks so much!

And FYI, our backend will be PHP, MYSQL and we plan to run this on a closed loop wireless LAN.