onboard GPS systems

I would think it all depends on who makes it, should be a name brand and a model on it somewhere, Pioneer, Kenwood, Alpine, JVC, Sony, Pyle, Dual, etc...
Some will provide free updates, others will charge you.
Depending on how old it is there may not even be any updates available, like cell phones, many manufacturers want to sell you the latest and greatest model, so they quit updating the older models.

Many of the newer units are updated by using a mini- or micro-SD card. You download the update (maps or software) from the manufacturer to the card, then plug it into the GPS.

My dingy came with a navigation system (which I really like). I bought the card just like emiddleb described and updated it. Real easy, but the card cost about $180.

I use CoPilot GPS, currently on an iPad Mini, which I Velcro to the steering wheel. It's always online, and downloads an update when needed. CoPilot is all on device, doesn't need a connection top work, best gps I ever had.

On my previous Pioneer unit, I bought the new CDs every three years.

I use my co pilots cell phone works good nuff for me. lol

We use a Garmin with all or routing done on the laptop and verified with Google Earth. Updates are free with life time maps. Up dates take forever and do the down load to an SD chip to get around lack of memory. The update cd for the Grand Cherokee in dash is $500 so guess what never gets updated.

Check out the GPSreview web site for tips and tricks for up dating the GPS.
GPS works where cells don't which is most places we go.

I've probably personally spent more than anyone in this forum on GPS technology...Trust me - I'm a pilot! :)

Anyhow - for cars, I've always enjoyed the Kenwood line. Alpine, Pioneer, Eclipse - they all have some form of premium product, but the nice thing about Kenwood has been their licensing and inclusion of Street Pilot Technology into their 2din NAV line. The downside is that updates on a dash mounted unit could always be a little slower or out of date than portables unless you have creative means for an update.

http://www.kenwood.com/ce/dnn1/na/en/dnn992/index.html

If recency of information is your deal, then Garmin Portables are probably best. You can't find an easier interface to use.

Iphones are fine and I use mine more than most...it's just...so inferior by comparison to what Garmin offers. The downside to Garmin is realtime context.

We don't use our in dash GPS. It would cost more to update twice it than a new portable unit...so we got a Garmin a Sam's Club with life time updates.