You can also program a Scan Gauge II to show data on the fly. I have mine setup for
overall mpg,
instant mpg,
miles driven today and
miles to empty gas tank
The instant mpg is very helpful in keeping my foot off the pedal and knowing when the transmission will downshift (which drops mpg like a rock).
My daily driver has a miles-to-empty function that's accurate enough to rely on . . . . and I do! But I wouldn't want to be stranded with a 20,000 lb vehicle and haven't really tested it (yet).
The wireless OBD scanner sounds pretty cool and may be the best solution if all you want are codes. I'm sure they have an Android app also.
Best,
- bob