WeChat (by Tencent) has similar feature, but you must first add people to friend list then chat. However this raise an interesting topic: How to securely verify that a device is indeed nearby and not spoofing it? You can spoof your GPS coordinates easily on Android at least.
Why would that be a problem? Your location should not be an identifying value but more or less a topic. Being able to set your parameters to some location somewhere and chat with "random people" there seems like a feature, not a bug.
On WeChat it happens that if you send a message to a 'nearby pretty girl', you get a link to some dodgy website back.
And before you call people who would send a message to a 'nearby pretty girl' naive. WeChat is in fact used a lot for hooking up with strangers.