I use an iphone to do some stuff on youtube but whats a good app i can use if i could do a speedrun on

Being 100% Honest last time i checked the recorder my friend used was banned off of the appstore, unless you want to jailbreak your iPhone than no

I'm on Android but I heard "Air Shou" is good for iOS

You could try reflector: http://www.airsquirrels.com/reflector/ Used it for a angry birds race once.

Depends on what exactly you are willing to do. If you want to record locally on the iPhone, and you don't want to/can't Jailbreak then AirShou. If you can jailbreak, Shou from Cydia (It is different than AirShou)

If you want to record on your PC, then you can use the integrated AirPlay feature on the phone, and use something like LonelyScreen on your PC (There is a lot of AirPlay servers for PC, but LonelyScreen is the one I know because it's free.)