I have a home cordless home phone with a bluetooth option, that lets me link whatever BT enabled cell phone I have (including iPhone) and dial out or receive calls on it.

Here's the link:
Bluetooth Cell Phone Device - Panasonic Link to Cell KX-TH1211 Bluetooth Cell Phone Device

I think a really cool iphone app for development would be one that does this exact same thing, but links up via iPhone BT with another BT cell phone, that gives you a dial interface on the iPhone.

The advantages of this would be huge. First off, it would end the cat and mouse game of unlocking.

Secondly, you could use your iPhone for virtually ANY service provider or radio technology (GSM, CDMA) or ANY carrier.

Why do I need this?

Well, ATT is not a suitable carrier for me, for obvious reasons. Further, TMobile has proven to be wholly unreliable in every capacity. They've shut my edge off arbitrarily more than once in an effort to get me to pay more money for new service plans. The coverage area is lacking. I just simply cannot rely on it anymore, especially for work when important calls come through.

I've switched providers to a new Straight Talk plan. It runs on Verizon's network. It's cheap ($45/month unlimited). Very reliable. But I have very limited choices of decent phones.

So I still carry my 3GS with me, as well as my new Straight Talk phone. I'm constantly looking up numbers in my old contact list and utilizing all the other functionality of the 3GS, but can't make calls.

So, I'm always carrying two phones anyway, in close proximity. I should only need to use one. I'd love to use my iphone only.

Can you make it happen for me?

I'd pay serious money for an app like this.

I'd think this would be pretty easy code, as it's proven technically possible already.