I use to work at Circuit City and I work at Staples now. To tell you the truth I'd go with Garmin they are the most user friendly.
The cheapest GPS units include some of the Tom Tom units with less features. Top recognized brands on the market include the Tom Tom GPS and the Garmin GPS units.
Best Buy sells several different types/sizes of GPS units. They sell portable as well as handheld units, which some people might refer to as pocket sized. http://www.bestbuy.com/site/Car-Audio-GPS/GPS-Navigation/abcat0301000.c?id=abcat0301000&searchterm=gps&searchresults=1
The Tom Tom GPS is clearly the best on the market, and will work for you for both walking and driving. You will just have to check it periodically to make sure it is working.
In 2008, the Garmin Nuvi 760 was considered one of the best GPS units on the market due to its user-friendly interface, accurate mapping, and reliable performance. It offered advanced features like Bluetooth connectivity and lane assist guidance.
The best non-GPS bike computer on the market is the Wahoo Elemnt Bolt.
The best GPS cycle computer with maps available on the market is the Garmin Edge 830.
The Acura in-car GPS units were the first to get traffic information overlaid on their GPS displays, and still are the best.
The Garmin Nuvi 880 is the best GPS unit out there. This is according to CNET, a technology review website.
Some of the best bike lock GPS options on the market include the Sherlock Bike Tracker, the Linka Smart Bike Lock, and the Spybike GPS Tracker. These devices can help you track your bike's location in case it gets stolen.
After searching amazon I found the Nextar C3 3.5-Inch GPS was labeled the best on the market. There aren't many differences between GPS systems to be honest, it's all about preference.
There are several GPS navigation units. To name a few of the popular units: Tomtom, Garmin, Kenwood, Motorola, and Magellan. You can find a full list of the top 5 here: http://reviews.cnet.com/best-gps/
The Garmin Nuvi 880 is widely considered to be the best automotive GPS on the market at this time.