Oh so texting works with the iPhone 5? Good to know. Now if the two would just play nice with displaying song text on the sync screen via bluetooth.
I don't think that is true. It requires that the Message Access Profile (MAP) be enabled in the bluetooth stack. It isn't a limitation of the hardware from iPhone 4 to iPhone 5, it is a limitation of the software. iOS 6 added the MAP profile, which I believe all iPhone 5's shipped with.
In short, you must upgrade your iPhone 4(s) to iOS 6 to use text messaging with it. I can't explain why Apple upgraded the bluetooth hardware with the original iPhone 4, but didn't enable MAP until very recently.
Disclaimer, I don't have an iPhone so I can't test these claims. Just information I've found while reading and researching how to get my Android device to work.