title: Web service for location data
body: <p>I'm trying to design a web service on Heroku that collects GPS locations from many people in regular time intervals.  Apart of keeping track of each person's location at any particular moment, I'd also like to be able to query who's within a certain range/radius.  </p>
  
  <p>I have an idea of how to do this using quad trees, but I just want to make sure there isn't an add-on service that already does this such that I won't be reinventing the wheel.</p>
  
  <p>Any help would be appreciated!</p>
  
  <p>Thanks!</p>