hand written signature

Hi Guys

I have a customer with a service business who wants to use a tablet to invoice their customers as they go from job to job. There are several wordpress plugins that could fit the bill. However some of their customers are corporate customers and require them get a hand written signature in the invioce at each location.

I have no experience with tablets and even less with written signatures in tablet PC’s. Does anyone know if this is possible? And is it possible from in wordpress?