Leo Grand considers himself lucky when the doorman at the luxury apartment building nearby lets him charge his Samsung Chromebook without issue.

Leo's app — Trees for Cars — just launched this morning, and the new coder needs to make sure his computer is ready to go for the day. The guys in the apartment building have been a great help; four months ago when Grand started this venture, it was warm outside. That, unfortunately, is no longer the case.

"Trees for Cars" is a mobile application that aims to save the environment by helping users carpool to their destinations, and Grand programmed the entire thing himself from the streets of Manhattan with just 16 weeks of coding lessons. It also provides information on how much CO 2 the user is saving with each ride which further encourages environmental awareness, creating within the app a healthy competition amongst users to save the most CO 2 .

Grand was approached by a young programmer named Patrick McConlogue in mid-August with a choice: Take $100 or take an opportunity to learn how to code. Grand, who had been homeless since 2011 after he lost his job at MetLife and was priced out of his neighborhood when a high-rise went up on the next block, didn't hesitate.

Please enable Javascript to watch this video WATCH: How Leo Learnt How To Code, Despite Being Homeless

He wanted to learn to code.

The two men met every weekday where Leo sleeps outside for an hour each morning. McConlogue taught Grand how to program using three used books from Amazon and a refurbished Chromebook McConlogue purchased for Grand online.

Business Insider spent a lot of time talking to the men back in the fall, and we even visited a coding class on what would be the coldest day of September. Grand talked a lot about his upcoming app (which, at the time, remained a secret), and how excited he was for its launch. There were naysayers who said this day would never come, but Grand, McConlogue, and thousands of people following their journey on Facebook had kept a positive outlook.

Now the app has arrived to the Apple Store and the Play Store for $.99.

Trees for Cars "Trees for Cars is a great way to build relationships, strengthen communities, help each-other financially and energy wise, all under the umbrella of saving the environment," Grand said in an official statement about the app.

Here's how it works: As a driver, simply pick a meeting address and the app will suggest nearby riders. Then, each rider and driver are only connected if they choose to mutually accept the invitations. The app tracks how much CO 2 was saved by the passengers who got rides with others.

All of the money the developers receive from this app goes to Grand, who will use it to help him further his programming education.

Here's a video of Leo talking about the app: