The iPad isn't a phone. It doesn'tr connect to the phone network as a phone and so it can't use SMS to send messages. It can only send messages via the internetusing the einternet implementation of iMessage.
Currently, only iOS5 deviceds ahve iMessage. Maybe Apple will make it available on other dvices, I don't know.
As to why it doesn't work between your wife's device and yours, you may have to be registered with iCloud. It's working fine between myself and my partner
This might help
Thank you for the link. It both explained and confirmed my thoughts about iMessage. I have checked that everything is turned on and we do have everything registered with iCloud (which should have nothing to do with this).
I am glad that it works for you. I still can't get it to work. Why not? Apple prides itself on "just working out of the box" and this app requires me to try and figure out more than I should have to. I could have stuck with Linux for this.
As I stated in my original post, there are some core capabilities Apple should have put into this. It shouldn't matter that it isn't a phone; the idea is to sent data from one device to another. Cell networks, data networks and WiFi should easily handle that.
This app reaches too few people and requires too much trouble to get working. Again, thank you for the link.
I agree with you. You see the same icon on both the iPhone and iPad one would think the same functionality would apply. I purchased an iPhone and iPad within weeks do one another, and as a first time Apple user I'm struck with the apparent arrogance of Apple. No Flash. iMeesage registering. How incredibly stupid. My way or the highway.