The original cover idea for my mystery novel Cache of Corpses simplified, with a snippet of topo map suggesting the location of a body inserted into the window of the enlarged GPS receiver. I think this'll work for the e-book version. Thanks to all for your suggestions.
Yesterday I finished applying all the hardcover publisher's edits to the electronic manuscript of Cache and have started sending it out to volunteer proofreaders. (If you volunteered but haven't been contacted, that's because I don't have your e-mail address; please send that to me.)