I bought TouchRetouch the other day cost 59 pence this is one simple app to use and why its this price i do not know, its a must have. Take a look at the site you will see just how easy it is to use, ever taken that picture of someone with a light post behind them looks like it is comeing out of there head, or phone wires running through the pic spoils the look.
Then get this app it will get rid of the stuff you do not want and you will not no it was there, i have spent hours editing pics in the past, this is like having harry potter wave his wand puff its gone.
Take a look at colorsplash to, turns your pics into black and white as you bring it into the app, then you can run your finger over any part and it brings back the color where you want it, i do a lot of woodturning so the backgrounds i can leave black and white and have the turning in the orig color. lots of possiblites.
Try youtube for info demos on all your apps.
ColorSplash - Fun and Intuitive Selective Colorization App for your iPhone and iPod Touch