Considering that Taïg Khris has jumped off the Eiffel Tower wearing roller blades, being an entrepreneur is big a step down the ladder in terms of adrenaline rushes.

But for Khris, 39, today will bring its own set of thrills when his company’s first app debuts in France with a goal that is daring in its own right. With the official launch of Onoff, Khris wants to separate your phone number from your smartphone, and change the way you think about using mobile devices.

“Technology is opening up more ways of using the smartphone,” Khris said. “We want to break up a lot of the established thinking about what your smartphone can do.”

I met Khris last December when I interviewed him on stage at LeWeb in Paris. The title of the talk: “What every entrepreneur can learn from extreme sports.”

Born in Algeria, Khris is a world-class inline skater, winning gold medals at the X Games while also becoming increasingly famous for his larger-than-life stunts. Perhaps his most famous was his leap in 2010 from the Eiffel Tower onto a ramp.

But Khris, always restless and looking for challenges, decided business would be his next plunge. He had the basic idea for Onoff a couple of years ago, but getting people to take him seriously required the same kind of relentlessness and persuasiveness he needed to convince Parisian authorities to let him build a giant ramp at the foot of the country’s most famous landmark.

Eventually, though, he did woo a core team of programmers and engineers to help him design and create Onoff.

Starting today, only in France, the app will be free to download for iOS or Android or Windows Phones. Once installed, users can sign up with their Facebook account.

Onoff lets a user instantly provision a new phone number — what Khris likes to call a “cloudnumber” — that is not connected to the SIM card in their phone. That new phone number comes with voicemail and SMS capability. And an important feature that Khris highlights is that the calls and SMS messages are carried over regular cellular networks, in partnership with phone companies, and not over the Internet like VoIP services such as Skype.

“The quality of a call through our app will be much higher than a VoIP call,” he insists.

The first number will be free for a trial period, and then the basic service will cost about $3.25 per month. Eventually, users will be able to upgrade to services that let them provision many numbers, rather than just one. So if you meet someone, you can create a phone number just for them, or maybe a small circle of friends or family.

If you lose your phone, or the battery dies, or you just decide to switch from an Android phone to an iPhone, all you have to do is download the app, log in, and all your phone numbers, contacts, and messages are right there. The goal for Khris is to separate your phone number from your SIM card.

“Having your number in the cloud will make a big difference,” he said. “It will really change the way you use your smartphone.”

Here’s a short demo of the service:

For now, Onoff has been funded by Khris and group of friends and acquaintances. In some cases, he let friends chip in a small investment just so they can be part of the company in case it really takes off, he said. Later this summer, he will seek more formal venture funding to expand the company beyond France and to grow it from its current size of 25 employees who are primarily based in Paris.

Khris insists that he’s not disrupting the telecom carriers. He emphasizes that to pull this off, he’ll need to sign them up as partners. In exchange for a partnership, carriers will share the revenue generated by the Onoff service.

That Khris has come this far with the idea, and managed to get so many people to take him seriously, is a testament to his determination. Building a global company remains a wildly ambitious goal. But he’s a hard person to bet against.

For a bit more color on Khris, check out my interview with him: