I want app for iPhone or iPad, which can search for people within 100 meters (probably need to use Bluetooth), and is able to exchange information with them or talk to them directly.
Does anyone know of such an app?
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Have you tried Bluetooth Chat?
With this little app you can chat via Bluetooth with other iPhone and iPod Touch (2nd Gen) users nearby.
Customer reviews are good, so it seems to be the solution you seek.
The problem with what you want to do is that the person recieving the information will need to have the app as well.
For instance you can try Walkie Talkie this lets you use Bluetooth to talk, however you cannot send not verbal information.
But for the whole purpose the iPhone has already got some of the features you require.
Yes, there is a web app that does just that, it is called DistaLab and is accessible from www.distalab.com.
It is only a web app, but I think they are going to release the app soon as it's getting quite a bit of attention.