You've likely been in the following situation. You get dinner with a friend at restaurant that only takes cash. You grab the bill and tell your friend to pay you back when he has some cash. Of course, then you have to wait until you see him next, and even then you'll likely forget about the $15.

Bump Pay, a new app being released today for the iPhone and Android phones, is all about making sure you get that money on the spot by using something people rarely forget at home - smartphones.

Similar to the regular Bump app, which lets users transfer photos and contact information, Bump Pay lets you tap or "bump" two smartphones together and transfer money right on the spot via PayPal. PayPal used to offer a similar feature in its app using Bump's technology, but removed it last month.

The new app uses the same technology in Bump's self-titled app, which has had over 80 million downloads since its release in 2010. A combination of the sensors in the phone and Bump's Cloud services allow the phones to communicate and then transfer the payment.

"We decided not to add this to our current offering because we wanted to make it as simple as possible so people understand how this works," Bump CEO and co-founder David Lieb told ABC News.

While there are other apps and services on the market, such as Square, that allow people to pay each other, Lieb said Bump is much easier.

"We love Square, but think they are attacking the merchant retail problem. We are trying to solve the person-to-person problem. We wanted to make it really, really frictionless. You bump phones and that is it."

And that really is it. You can log into your PayPal account in the app, then type the amount of money you want to send, and then tap it to another phone that is running the same app. Unfortunately, you can only pay one person at the same time, which means you can't start splitting bills more than two ways.

Bump Pay is available now for free from the Apple App Store; the Android version will be coming soon.. Hey, maybe you'll get that $15 back for dinner after all.