cheapest monthly service for 2 iphones?

[archer75]

2 iphones on the family plan are $109.99/month and that's just not going to fly.
After our 2 year contract ended with out current phones on AT&T I switched them to pre pay. We just don't use them much and we have a land line. We get unreliable cell service in our neighborhood so we have to have a land line. I pretty much leave my phone in my truck. I can't use it at work anyways and if i'm out and about and wondering if the wife needs anything from the store, if there is an emergency or something can't wait till I get home, that's the only times I use it.
So what is the cheapest way to get service on the iphone? I have access to wi-fi at home and at work. Much of my home time is covered in wi-fi. I imagine with a nice VOIP app on it it would satisfy my phone needs. Which makes me think an ipod touch would be nice. Though I would like GPS or GPS like features.
If the iphone has a stronger signal than our current phones it could replace our landline. But that's VOIP and is only $15/month so it's not a big deal.
And i'm really intrested in the apps to replace my pocket pc. And since my ipod broke i've been using a shuffle to listen to my podcasts.

Ok, i'm rambling I know. So give me your advice. Get an ipod touch for me and the wife and continue using our current prepaid cell phones or get two iphones?
I hear I can activate them through a funky process of providing a bogus SS number and set them as pre pay and then add an unlimited data plan? Is this true? Is this officially supported by AT&T? Could I still transfer our phone numbers to these phones? I know i'll loose visual voicemail, not a big deal. But i'd still like access to apps, official or otherwise. As well as GPS or GPS like features.

[Poseidon79]

Skype VOIP is $3 a month and the app to use it with is FRING.