I have an iPhone with a data plan and want to stay in touch with someone with an iPhone without a data plan. The iPhone without a data plan pretty much always has WiFi though.

Email is ok but slow because "Push" with Yahoo doesn't actually work (even though some users here say it does, it seems that the web is full of reports of people complaining that Yahoo! doesn't actually push as advertised to iPhone's Mail App).

TXTs are getting costly but are more instant - the other advantage of TXT is that you get a decent volume SMS alert tone. The "New Mail" tone is bloody pathetic!!

Anyway is there any App that will allow instant messenging? IM+ and Skype both are pretty cumbersome to use for this purpose, not to mention the drain on battery if left signed in. IM+ doesn't even seem to keep connections after you jump out of it even though it says it will.

Thanks :)