Some flight computers[1] for flight planning. While a real flight computer costs about $10 and up new, you could use an Android app as well (in the simulator ).
- Free E6B by Intineo - This one does what it says on the box. Simple and easy to use.
- Flight Computer Sim by Diego Rodrigues - This one is a bot more refined and and can be zoomed as well. More than 100000 downloads.
- Rule Slide by Mastermodeling - This one I have not tested, but it appears to emulate a Russian sliding rule for navigation (and thus is in Russian).
A barometric altimeter that can be set in inHg (very few altimeter apps can be set for a pressure).
- Pressure Altimeter by Edward Falk - God for demonstrating how a pressure altimeter works, transition altitude (on ascent) and transition level (on descent).
[1] Stefan Vorkoetter (August 25, 2006), A Tale of Two Whiz Wheels: E6-B versus CR Wind Solutions, stefanv.com is a good introduction to the wind calculations on the E-6B and CR style flight computers.