I think that every airfield should have free wifi internet.
However, looking at going further afield, the only solution to streamlined flight planning is a laptop with a GSM/GPRS card. The access is not cheap but one doesn't need much data. I spend a few quid per flight on average and that includes filing an ICAO flight plan and faxing the GAR form to all three numbers.
I don't know about supported GPS types for Navbox Pro - have a look at
www.navbox.nl
As regards dead reckoning, it works quite well because the aircraft speed is so (normally!) much higher than the wind, and if the visibility is OK then one can see terrain features a few miles away, and one can correct the track accordingly well before reaching the waypoint. I think that human errors are a bigger problem in reality, e.g. messing up the stopwatch, an arithmetic error in the plog, etc.
I also think that training could be much improved when it comes to selection of waypoints. It's no use picking a lake, when there is another similar one 10 miles away. One should look for unusual features, unusual patterns in road/railway intersections, etc. Same with towns and villages, so many look the same.