Is there an alternative to Adress Book that works both on a Macbook or Imac *and* on Iphone? Is there an alternative to Adress Book that works both on a Macbook or Imac and on Iphone? I always get stuck on managing contact groups on all my apple devices. Or is there a strategy to keep contacts data consistent on 3 apple devices at the same time. I'd rather like to do it without cloud services due to privacy concerns.

edit for clarification:

I use an imac (Snow Leopoard, early 2008) at home, a MBP (early 2010, Lion) for work and an Iphone 4 (iOS 5).

When i try to sync my contacts or groups of contacts from the iPhone to the MBP, it's not working. But the other way round it's possible, although i have to overwrite all existing contacts.

With the iMac it works great. Both ways.
What about Cobook? 

http://www.cobookapp.com

There's a mac app and an iPhone app
AND 
it's free!