I'm using Google Voice and Callcentric as my service providers on an Obihai110.
There is a service called PopMoney which allows for the sending and receiving of small sums of money.
https://secure2.popmoney.com/richux/faces/base/popmoney/prelogin/searchBank.xhtml
Reading the FAQ just now, I noticed that they require both an e-mail address AND a U.S.-based mobile phone number. I presume they send a text message to one's mobile phone to notify users of in-coming/out-going funds.
I don't have a U.S.-based mobile phone number for receiving text messages. I do have a U.S.-based Google Voice number. Can a Google Voice number handle an in-coming text message directed at a mobile phone?