Why did Tommy do this? In his own words, "Pokémon Go has gotten a lot of people to come out of their houses, walk around their street at night. I don't want to do that. I'm lazy and I'm a programmer, so I think there's a better way to do it."
In his easy to follow tutorial, Tommy teaches you how to spoof the GPS on the iPhone and change your location without actually having to move from your computer. According to Tommy, anyone can do this as long as they have a Mac.
This seems complicated, but it's actually so easy and Tommy does an excellent job of walking you through the steps.
All you have to do is download a free program called Xcode onto your Mac. Plug your iPhone into your computer. Pick your iPhone as one of your devices. Then follow a series of very simple steps provided by Tommy.
After walking you through a handful of simple directions, Tommy plays Pokémon Go in London, England from his house in Southern California. He catches a Rattata then heads to Hawaii to hunt for more Pokémon without having to get out of his chair. IT. IS. AWESOME.
Because of the popularity of his first video, Tommy added a few more tutorials for advanced users. I wouldn't consider myself a techie in the slightest, but I was able to follow along pretty easily. So make sure to check those out as well.