There are plenty of poor people who cant afford to make mobile phone calls or send sms messages. With this they would at least had some way to do so.
Say there is one mobile phone in the village (powered by say a solar panel). A person could just borrow that or rent it for a moment, to send some important message. Say to find out what the price of milk is today at the market in the next village. (If they cant read or write then they could get that one kid that can, to do it for them)
Small thing like this could create all kinds of new opportunities.