I am particularly looking for a competitor which has the approach plates loaded.
For Europe, there is only one way of getting electronic approach plates which are georeferenced i.e. show the aircraft position on the plate: Jeppview.
The price depends on the desired coverage and is pretty steep. It is aimed at corporate and upwards.
JV will run on any Windoze machine, and for in-flight use you want a tablet computer running the XP Tablet O/S.
If you are skint / not fussy about presentation then you can download most European plates free from the Eurocontrol EAD site. Most of these are a bit crap though - most seem to have been drafted deliberately to not compete with Jeppesen
But they are clearly usable.
As Anton says, once you have a tablet running windoze, the world is your oyster as regards software. You can run Memory Map for the UK CAA charts (three to cover the UK; cost has recently dropped to about £20 each). Oziexplorer can run a huge range of maps of all kinds (including plenty of "unofficially sourced" VFR aviation charts) taking advantage of the vast underground map distribution network (on P2P) which is driven by the tight copyright restrictions on all maps in Europe. And you can do stuff like internet / weather / email using a satellite phone.
I am suprised Garmin keep their units closed-architecture because the 696, with its decent size screen, could do quite a lot.