Cisco have announced a 7 inch Android tablet computer aimed at business. The Cisco Cius docks with a desktop IP phone, making a device reminiscent of 1990s computer/phone and video phone units, which did not prove to be popular. But the Cius can be removed and used as a wireless tablet computer. It will be interesting to see if this catches on.
Other tablet computers come with a docking station and could be placed alongside an IP phone. Also these tablet computers have IP phone functionality built in and could be used as a very functional desktop phone, with the addition of a low cost handset.
One flaw in the Cius design is that it appears to have no physical keyboard on the phone handset. The intention appears to be that the tablet touch screen is used as the dialing pad. This is a poor design choice, as phone keypads can be dialed quickly without the operator looking at it and receive heavy use which is likely to wear out the touch screen.