I use a Garmin 60CSx model that I like a lot. The stub antenna really helps lock in satellites when the sky is obscured by trees or terrain. Cost for these is around $300 or so for a similar model.
I also use a Trimble device that is even more accurate (under a meter) but at close to $5k I don't recommend it for the average trail rider.
In regards to a device that would allow family or friends to know your location. You might try:
SPOT - These have been out for a few years now and can send an emergency signal to an orbiting satellite to summon emergency services if needed. I personally know a rider that had and used a SPOT device after she was kicked in the head when putting hobbles on about 20 miles into the backcountry. Life Flight flew her out and she's fine now.
The SPOTis essentially one way communications. You can send messages out but not receive any. Costs for the SPOT are "I think" in the $150 range with a $10 per month plan expense.
InReach - This is a new product that has 2 way communications and I think is way cool. The InReach does everything that the SPOT does but also allows people at home to contact you (an example would be an emergency at home while you're camping far into the back country). The device and the plans for these are somewhat more expensive than the SPOT, but then you also get to receive msgs.
Another nifty and very low cost option that I've been playing with recently are apps for your smart phone. If you have an Iphone or android phone you have a GPS chip inside that can operate without a cell signal. There are numerous apps available that will let you use this bit of technology.
I've been pretty pleased with the ViewRanger app so far over some of the others. Before you leave the barn you can download topo maps of the area you plan on riding in and then refer back to that while on the trail. Of course you can also save the tracks, enter waypoints, ect. Just like with a regular GPS unit. The accuracy seems to be quite good. I haven't been more than a few meters off during my tests to date. At only $8 dollars it's worth a look if you already have a smart phone.
Of course, I would be remiss without saying that the very best tool is a traditional map and compass and the knowledge to use them. High tech is cool but certainly not a replacement for piece of paper and a magnet on a stick
Hope this helps.