A GMaps page in Ruby+Sinatra that represents JSON information

I've got a clear JSON file that has information about spots. I need some of that info to be put in a map and updated every 30 seconds. So to keep things compact and quick, I require it to be coded in Ruby and fit in a single file using the Sinatra gem plus in-file HTML; JS/CSS can go in a file appart. You do not need to give it style yourself. I will provide your with the API info you require. The JSON file looks like: {"stations":[{"id":1,"uid":233, "risk":"RISK","suggestion":"4","name":"NAME",""latitude":39.497128187401,"longitude":-0.369528093405798,"open":true,"total_slots":15,"empty_slots":2,"full_slots":13},...}