I don't know about an ipod, but here are the issues when I've tried to use my smart phone instead of a $30 dedicated recorder:
-- Battery life (hours vs. weeks)
-- Recording quality (hard to hear vs. crystal clear)
-- Set and forget (something is going to stop the recording vs. it never misses a thing)
On all three issues, the $30 dedicated recorder kicks smart phone butt. When I realize that I have forgotten my recorder, my phone does in a pinch, but it is impractical to turn it on and let it run, so, in an encounter, I'd have to turn it on. That opportunity might not present itself.
Get a dedicated recorder. Turn it one when you leave the house. If nothing happens, delete the recording when you get home. Replace the batteries every few weeks.