Expanding on what I said, a lot of smartphone editors are really basic. Little better than iMovie. Best one I've seen is Pinnacle Studio for iPad. At least then you can work with a decent sized screen. As I said, it's doable but far from ideal. Like trying to drive a car with square wheels.
I made a 20min travel doc about five years ago in college. It has three segments. Each segment is made up of dozens of shots. It took about two weeks to edit the thing. A lot of 16 hour days. That was a collaborative project as well.
Plus if you want to add music or effects, you'd have to import those to your phone. There's just a lot of information to manage on such a small screen with such a limited control interface. You have to keep all your files on the same device too.
If you need a good, cheap, professional editing program, try LightWorks. Their public betas are free. It has a steep learning curve though. Especially if you're trained on other NLE software. You can also use Premiere Pro CC, which is $20/mo. $240 a year isn't bad considering how much a lot of other standalone products cost.
Have a Mac, Final Cut X is the only program you should be using.
yeah you definitely want to use a desktop. even then editing the first 2 minutes of intro on mine was a 16 hour day.
People have no idea how much work goes into a half hour of television.
I've edited news stories for air on a smartphone before. Back when the iPhone 4 was new we were kind of pushing for more mobile journalism.
We were using the Dejero app at one time for live hits. It's great. Big car crash, you can rush a reporter out there with only a phone and a small tripod. Streams it through LTE back to the station. They had a GoBox too for ENG camera hits.
That was unheard of just a couple of years ago. Before you needed a broadcast truck or mini-mobile to handle that. Usually with a microwave transmitter, or at minimum an ethernet connection.