Any device which can tell you Lat (L) and Longitude (Lo) can be used to calculate straight line distances, speed, and distance travelled and perhaps some averages. Sounds like you'd like a bit more such as electronic chart plotting ?
Other things to consider -
* SPOT Locator for rescuehttp://www.globalcomsatphone.com/spot/
* VHF Radio (some have locator support)http://www.marine-electronics-reviews.com/handheld-vhf-radio.html
* iPhone now has an app made by Fugawi that has maps etc. http://www.fugawi.com/web/x-traverse/navionics_faq.htm
PS> remove your email address - or it's going to be a spam magnet.