I'll add one answer to this already a bit dated question, since things have developed a bit in the last year or so.
You can install R locally on an Android device using the GNURoot software that is available from the Google Play. Despite it's name, GNURoot does not require rooting the device. I outlined the installation process in a few more details in my blog at http://www.r-ohjelmointi.org/?p=1434.
There is also R-Fiddle (http://www.r-fiddle.org/) that you can use through browser, and if you can connect to a WLAN while on a journey, it might be worth testing, also.
