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.
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.