ichat application for android
I have a Nexus 4, Nexus 7, and will soon probably buy a 10 inch android tablet. We have a friend who for some reason has an iPad, and we'd like to be able to chat with her. She uses an application called iChat (apologies, I know almost nothing about apple stuff). Is there a free application for android (with a downloadable apk I can find) that will allow us to communicate with iChat?
One of the things I like best android is that it doesn't require any accounts, and I would not be interested in apps that require an account with e.g. google play, or any other entity beyond what is required to operate with the ichat servers.