Replace Garmin Streetpilot 2720 with Kindle Fire 8.9

You mention that cellular connections can be an issue but then blow off the fact that downloading the maps in advance completely negates that as being as issue. The phone will work just as well with or without a cellular signal as it is fully GPS functional at all times. If you are not disciplined enough to take a couple of minutes to download your maps I can't imagine how old the mapping program in your GPS must be when that can take an hour or two to fully download and update.