Dustin,
You can run KoBoCollect even on very low-grade Android phones. It is not very demanding.
You want to make sure you are buying unlocked phones, which can be found on Amazon, NewEgg, etc. for less than $100.
Make sure the phone comes with an SDcard, or you buy one separately.
I haven't bought anything from there, but friends swear by it.
KoBoCollect does not run on iPhone. Sorry.
If Arcpad will run on your Android phone, it can also run KoBo. I'm not sure what you mean by "in conjunction", but there is no interactivity. KoBo does save it's data as simple XML files, so if you can import them into Arcpad, you might be getting somewhere.
~Neil Hendrick