I was about to say the same thing. The GPS on my 'smart' phone is pretty accurate and there are quite a few navigation apps out there for you to chose from.I prefer the gps on my phone. Gps on any smart phone is the same and it's already covered in my data plan on my iPhone 4 and was when I had the I3 as well and my sons phone is not an iPhone but a smart phone and is loaded with the same gps system.
Tom toms are generally really reliable.. I havent ever had problems with them..My sister and brother both have navigation units and its pretty handy, so I'm thinking about getting one. I think they both have Tomtoms, should I go for that or do you have any suggestions?