[rjzzleep]

not sure if there's an ios version(there is an android app), but if you don't edit the todo.txt in a normal editor normally you might want to take a look at taskwarrior http://taskwarrior.org/projects/show/taskwarrior

it has import scripts from several things including todo.sh, and several export scripts including ical. there's a decent third party android app if you really want that.

it has task undo support, and generally seems much more powerful than todo.sh.

obviously main advantage of todo.sh is that you can edit the file in a plain text editor.