Diesel Conversion Gauge Options

[brimc]

I have been searching for some time on the interweb for great info and advice on my Cummins Swap. Recently, I have been back and forth on Gauges. I do not want to keep any of the stock Chev gauges. I do want to have all the needed info when running down the road ie; Boost, fuel, EGT, oil, water, volts, fuel level, etc. and believe that will all be a no brainer. Now I have come across GPS Speedo's. This makes perfect sense to me because no speed senders on swapped in trannys or axles and axle ratio and tire size will not affect it. I also need a tach and have read several different ways of running all sorts of different setups. I found a GPS Speedo and tach combo setup from speedhut. Is there any reason why this type of setup would not be good? There are pricey, like close to $400, but they look good and they will be accurate. Guess I an looking for pro-cons from other that have tried this or just different opinions?