Why not go the whole hog, and get a small sextant? (OK, it won't fit in the wallet.)<br><br>My girlfriend got me a small one last Christmas, and I've had great fun mucking around with it. Not entirely sure I want to replace the GPS yet, but the US gov can switch off the GPS; the Sun and stars are a little harder to get at (barring smoke grenades :-) ).<br><br>And as a bonus for a math geek, you get to play with lots of sinhs and coshs too! What more could you want?