What do I mean by that? Well, if you start talking to someone you like, you have to arrange a time to meet them. This is because these websites only match you on general location (ie you are both in the same city).
Another interpretation of this would be to focus less on finding the "perfect" match, and more on finding someone who is physically close enough to meet right now.
Such an app could work as follows:
You are connected to another random nearby user via chat. If there's enough people using the app, you could begin to match people by interests, and share this matched interest with both people.
If both people strike it off and want to meet, they could choose to share their location with each other to meet up in person.
It's really that simple. But such a conversation starter/dating system could be incredibly powerful because people crave human connection, and this would dramatically reduce barriers, increasing the speed at which you can discover and meet new people.
Imagine going alone to a sporting event or a concert, and using the app while you're in line to find someone who shares the interest of that sport/musician, then enjoying the event with them as a first date, or even just striking off a friendship.
As someone who has used several dating sites before and found them all lacking, I'd be happy to be one of your first users if you build such a dating site. Let us know what you think in the comments!