Well this is an idea that I would like to share with all so that my dream can be realized. So here is the idea.
Now that we have mobiles with GPS we should make use of it. So now you have this messenger which would update your position in your IM every time you move over 100m or something. I am assuming that either the GPS now or sooner will be accurate to something like few meters. So when you have some of your friends around, you know that they are. Cool dont u think?
Here are options to make it happen.
1. Send update about the location to all/selected your buddies.
Pro: Simple and effective
Cons: No Privacy and your exact location is known to all.
2. Server gets updates and it pings you about friends close to you
Pro: Agains simple and effective
Cons: Requires server services. You location data is on a central server and this is a possible privacy risk.
3. Each person broadcasts a location to all his friends which is nearly correct. Now this nearly is something debatable but I would suggest it would be something like near in the range of a kilometer. If some other friends of yours is in location close to you, you respond by sending a still more accurate location. This step can be repeated several times so that friends who are actually close can know without actually revealing the true location unless they are truely close to each other.
Pro: Effective with privacy taken care.
Con: Complicated and can be wrong at times if the algo is imperfect.
Now I propose we use the third option along with Jabber perhaps and make a good instant messenger for cell phones. Can we have gang doing it during the Barcamp Bangalore 6. Can we just add this over an existing open source project. Do let me know if you are interested or have other ideas.