There are many portable GPS for car units out there, but Garmin Nuvi GPS devices are the best to use in cars
( You can visit their website here ). There are good reviews and feedbacks how Garmin Nuvi GPS devices works well. I recommend Garmin Nuvi 3790T which it is one of the thinnest and lightest portable GPS (where it looks like an iPhone).
It has a very good design and the voice command works pretty well and the traffic data are free as well as Bluetooth feature.
You can a take look here : Garmin Nuvi 3790T
If you want a cheap GPS navigator, Garmin Nuvi 265WT is a good one for your car. It offers several high-end features for an affordable price.
Take a look it here : Garmin Nuvi 265WT
Hope this can help you.
Some of the best Portable GPS for your car are:
1. Garmin Nuvi 3490LMT GPS Receiver – It has a very thin chassis but consists of high MSRP for the price of $325.55-$399.99.
2. TomTom GO Live 1535M – It uses an automatic twitter tweets to keep you posted with a price of $199.99-$249.95.
3. Garmin Nuvo 50 – The screen size is smaller now but offers the same functionality for a price of $114.99-$149.99.
4. Magellan RoadMate 5175T-LM – It offers few features that will help the users plan their vacations and explore different cities with a price of $210.95-$224.91.
5. TomTom Via 1535 – It has a lifetime map and traffic updates so you are always up-to-date for a price of $219.99.