What about virtual phones?
This is a very interesting product both from a business use and a digital forensics perspective.
If the data is properly secured and encrypted, then this could be an excellent option for many businesses and those individuals that don't want two separate phones. I would assume that this would utilize a lot of data and always require an active connection.
From a Digital Forensic Examiners perspective, this could cause a lot of issues if this concept is easy to implement by different providers that offer it as a anti-forensic solution.