I know metalmudder was available for the iphone at one point. It's not exceedingly powerful, but the full version of it is what I used to use on my mac before I switched to something else. Not sure if it's still being developed (the website for all of it disappeared last time I looked) but you might still be able to get the app for your iphone.

Written by my hand on the 2nd of Midwinter, in the year 1251.