We've been playing with a cut of GPS Navigator on our myTouch recently, and it delivers a totally usable car navigation experience -- a perfect complement to the comprehensive pedestrian capabilities of Google Maps. Most of the warnings from our G1-based review of the application carry over here -- you need true GPS reception, not merely cellular triangulation, so your phone will need a view of the sky to have a shot at picking up satellites (this also means that getting a location lock is a more time-consuming process, though it typically didn't take longer than a few seconds to do its thing). We're not digging how the colored lines that convey traffic information on highways flash; we'd rather they just stayed a solid color, the way most GPS systems handle it. We also found that the menus are a little wonky -- bringing your finger in contact with a menu item and swiping up or down to scroll would occasionally trigger the first item you touched, which ends up being a fairly annoying bug in practice. All told, though, if you can justify the expense, your $10 a month is going to net you a genuinely reasonable way to consolidate all of your help-me-I'm-lost needs -- whether by foot or by car -- into a single device.
TeleNav GPS Navigator comes to T-Mobile's myTouch 3G