Tell me, if no one responds to your beep - is there a return of tokens?
No. But as the app gains more and more users, the chances of no response for each beep will be lower and lower - down to almost zero. It can be zero because a beep can reach a radius of 1-5 miles of the location it's sent to, which is a 2-10 miles diameter. Certain locations will have millions of people within this range - and you're likely to find at least a few who can help you out. Also the price per beep is very low, at about $0.10 - $0.50 each, to reach millions of people.
If only you do not need help in something illegal or just strange. Then most likely no one will want to help you with this. But these are your problems.