Phone Play?

Hello everybody. I was recently asked if I offer phone play. I have never even thought of offering this and I have not seen anybody that has it advertised anywhere. I think that is something that I would like to try. Can anybody give me any information on this? I would like to know how I can get it started. What would be the best way to take care of the donation? What donation for what length of time would be reasonable? Would any of the TER hobbyists be interested in this type of thing? Are there any providers that can give me some advice?