If you like Tomtom and have a smart phone, you can buy a version for that. You’ll never need to pay for map updates either (unlike with the tomtom units). It’s something I’ll be considering when my one bites the dust.
If you have a smart phone you can get Nav mi for free. It holds the maps on the phone so it doesn’t need a constant mobile signal, and the maps for foreign lands are free too. It stopped me buying a separate sat nav.
The only problem when I use my Samsung S3 for navigation (using the Google nav) is that it’s too quite. It’s OK at lower speeds, but almost inaudible at speed with background noise. I guess a blue tooth speaker would do the job. My TomTom is obviously about 5 times the width, but has a nice big speaker in it.