if you run megasquirt, you can use any Android device to create a fully customized dash display including all running engine parameters. From what I see here that is the easiest route to go, I am unclear how these other apps interface with the engine data. See here
http://www.tunerstudio.com/index.php/shadowdashmsmenu
You can make all sorts of dashboards with all sorts of graphics and every engine parameter you can think of and you can use the phones internal GPS or external GPS for g's, performance, etc. Its really quite impressive.
As I don't own any devices, I'm not sure how boot up time and charging would work in a car situation, but again from what I"ve seen this is one of the best solutions out there. Megasquirt can be a little more work to get installed and running because they don't sell as many canned solutions, but anyone here that is a hot rodder can do it no problem and diyautotune.com has made it a lot easier, and if you are familiar only with older MS installs you might be amazed what it now supports, I cannot really think of anything Holley, FAST, etc. offer that is not available in MS.
I'm running my car with full sequential low impedance injection, crank trigger COP ignition, knock sensing, boost control, etc.