Create a Mobile Website

I'm looking for someone that can make a webapp that will allow it to post message on their location and those messages will be visible only if we are near this location (75m around the message location). The location will be get by the phone current location or the current wifi connection. There will be a map that will show each public message on it with a pin and when we will click on it, it will show the message. If the message is public but hidden if will be shown only if we are in the 75m range around the message location, so it won't be visible on the map until you viewed it (keep on it on record with a long duration cookie). If the message is private the user that left the message need to put a password on his message. When the message is private the user need to be near the message to view it and has the password to read it.