Wish You could search for a suitable GPS tracklog published by someone else... In fact, these are all onhand since the latest (silent, as usual) upgrade to Google Maps for Mobile (GMM). Now you can display user contents with routes (so called lineStrings) and folder structures, as well. There are sites providing complete networks of hiking trails in kml format. Just search for the URL of the kml in GMM, and follow the line with your GPS-enabled cellular phone.
Pls note that all this is only available in v2.2.0, on J2ME platform, currently.
Give it a try here