SayHi seems to replicate WhosHere. The plus side of it is that it has a map function so you're able to see how many users are currently online. The downside of the app is that it uses your exact GPS location which might not go down with some users (ie. using the app at home/office).
Also, there are point rewards that you get for completing your profile and using the app frequently. You can use these points to contacting users that have a hot status or use to send gifts - you have the option to buy points but if you use it enough then put that credit card away :)