I think this device can only succeed if the price is very very competitive.

If it was a similar price to the Asus transformer + dock and if the phone was actually a good hackable Android device, then it could attract a lot of sales.

If the price is too high, it is not worth it because if you break the phone, you lose your tablet functionality as well. If the price is high, then consumers may as well just get two separate devices that are both good at what they do. It's not like a phone is a burden to carry. The tablet screen is still as big as a normal tablet.

So hopefully the price is in the Asus Transformer range.. then it'd certainly throw a spanner into the current tablet market. Tablet + phone for the price of a good tablet would certainly be an attractive prospect.