It’s a cool idea Stephen. Better to upcycle technology than toss it where possible. Off the top of my head:
– Cases and accessories can be got for cheap, depending on how popular that particular handset was. You’ll want to hurry though.
– Cheaper than buying a new GPS outright.
– Larger screen and touch capacity.
– More apps available.
– Cellular voice and data capable if you choose to go with a pay as you go plan and are in range.
– Much less rugged than a dedicated GPS unit.
– Battery capacity and power management options are much more hands on and depend on the OS.
– GPS antenna probably less sensitive.
– Application options depend greatly on handset OS: iOS vs Android. I think there’s more options in Google Play.
– Data storage capacity depends on handset: you’re better off with Android handset that supports Micro-SD expansion for additional map data.
I’m a tech guy so this seems like a fun project. If you’re not a tech person, you may (understandably) lose patience with the process.