Not sure how long it's been around, but I've just noticed that SP1 is available for the Navman S-Series. Updated mine last night with no problems.
You can download it from here:
http://www.navman.com/Navman/Templat...t____4407.aspx
I've not come across a changelog yet to find out what it changes / fixes, but noticed at least one thing on the support site -
"(254) When on a Phone call on my S Series, I can hear the other person clearly, but they can't hear me?
- Content
Please ensure that you have the latest Service Pack installed on to the device."
...I'd imagine it fixes more than just that though.