What Google Talk compatible iOS apps can I recommend to my friends? What good Google Talk (or in general: XMPP) apps can I recommend to my non-Android friends (especially iPhone users)?

I'm fed up using many different apps to chat with some of my contacts. I just want to 'talk' to any of them with that single solution.

Google Talk's usefulness increases by network effects, i.e. can you reach all your contacts (who may use iOS (iPhone), Windows Phone, Blackberry, others) with one single solution?

Existing solutions and what I don't like about them:  


WhatsApp (proprietary, paid app, battery hog?, has privacy concerns)
eMail (pretty much ok, but not that realtime)
SMS (needs GSM, costs too much, no added value)
Facebook chat (proprietary, battery hog?, privacy concerns, not all want to sign up)
Skype chat (proprietary, battery hog?, privacy concerns)
iMessage (proprietary, incompatible with Android?)


If you have too many of those apps installed you will see a difference in battery life in the end. Google Talk is already there and connected either way, so I prefer this (and not WhatsApp).

Side note for iOS: iOS' push notification system seems to be the reason why the decent apps there are paid apps. (Need to relogin every 7 days to keep push messages alive and such, i don't really know).

PS:
 - There's a way to encrypt Talk messages, so it's not a privacy concern
 - is Talk open: Yes (it's XMPP). I have friends with accounts on their own servers that i 'talk' to
 - You can use 3rd party Jabber clients to login to Talk
Apple iOS
No official native solution by Google (except for the safari web-app with a subpar user experience)
Beware: All 3rd party providers seem to need your friend's plain google password to be able to offer push support (not just their app)! All have some sort of session timeout for push notifications (when the app is in background): Needs a relogin after that timeout (eww!).
3rd party apps I found:

IM+ Pro, free, ad supported, push with unknown session timeout
IM+, 9.99$, no ads and longer push session timeouts as above. Good reviews.
BeejiveIM for GTalk: free, push session timeout up to 7 days, no voice/video
Chat for Google Talk Pro: 0.99$, push with unknown session timeout, noticed bad reviews in Germany, good in US though

Windows Phone
todo
BlackBerry
has good support, download here
Symbian
todo
Bada
todo
Send me your findings, I'll happily include them here.