Can i create a document that people can sign on a touch screen?

I teach a basic computer class every two weeks and we have people sign paper agreements afterwards, I would like to take these agreements and put them on the computers they are using so that i can have them sign right on the Touchscreen using open office, or adobe, and email them directly to me. I need help understanding this process and the legality of this type of electronic signature. Im just trying to save paper, space and time! Also i would like to put these onto a tablet pc in the future. Any help on this would be greatly appreciated!! Thanks in advance guys!