Comment DR works for only a limited time (Score 1) 3
Using cheap gyros/accels will give you good DR accuracy for about a minute at driving speeds. Anything more than that requires an order of magnitude increase in the cost of the sensors. The costs will come down with time, but don't expect the GPS free option on your cell phone to give you much benefit in the near term.
Beta Sucks - and that is also not likely to change