The Five hand sign app on Android and Apple Watch. Five Like a lot of Polish 17-year-olds, Mateusz Mach is into hip-hop.

"It is something I identify with," Mach says.

Unlike a lot of Polish 17-year-olds, he decided to turn his appreciation into an app business. After six months of work, he released Five, a messaging app for Android, iPhone, and Apple Watch that lets you and your friends throw one another custom hand signs, like the kind rappers throw.

It's meant to be quick, easy, and above all, fun. Mach says his friends use the app to tell one another how far away they are, using a commonly accepted translation for each hand signal. You can even send your custom signs via Facebook Messenger.

"It's faster than typing," Mach says.

It's a little bit like Yo.

"We are better than Yo," Mach says. "Definitely better than Yo."

Five founder Mateusz Mach Mach Mach and a team of two other contract coders spent the past six months working on Five, with the funding coming from a local investor for whom Mach had done some work before. His previous app, Sagepark.pl, which is currently down, had 10,000 users at its peak, Mach says.

The thing is that this silly app is finding some real-world use, according to the feedback Mach is getting from his users. On the Apple Watch, using hand signals lets you convey more meaning without an onlooker being able to guess what you're saying.

And perhaps more important, it's a really great engine for communicating in International Sign Language (ISL). Mach says he has heard from deaf users who are using it to quickly communicate in a way that makes sense to them.

To that end, Mach is working on building in an ISL dictionary into the Five app, to quickly select words and their equivalents. If that works out, Mach isn't ruling out the possibility of making Five into a more complete ISL translator.

For now, Mach is splitting his time between working on Five and his time studying at an International Baccalaureate (IB) school — when I spoke to him, he was staying up late in his dorm.

In the future, Mach is taking Five on the road, preparing to show it off to customers and investors at the coming Bitspiration Festival in Warsaw, Poland.

He knows he wants a career in technology, and he certainly wouldn't mind if Five is the engine that gets him there.

"That might be cool, yeah," Mach says. "If only I can get money."