skydemon
I have used the Viliv x70. This is a full fuctioning pc tablet with built in 3g and GPS recievers. The screen is 7" and is sun readable. It works very well indeed and I find the ablity to view Notams, Metars and Taffs whilst planning and in flight puts this device with skydemon software way ahead of my 496. Another feature which I have found to be a revelation is being able to veiw airspace ahead and above in profile whilst in flight.
The only downside is price. This is not a cheap import sold on ebay and will cost a minimum of £600. Also it is a tad large compared to other gps devices so thought has to be given to mounting. I use a powerful suction device from ram mounts.