Unfortunately, we are at a time when technologies are slowly merging and you have to pick what works best for how you travel.
My son has just bought a camera that has a GPS built into it. It shows your coords on the screen and will collect tracks even when turned off. It burns batteries like crazy!
They have GPS's with cameras (I know Garmin makes a few).
My iphone does all of the above but rather badly IMO (crappy GPS receiver, crappy camera, crappy battery life)
My Spot (and my new inReach) can send emails and texts and possibly get me rescued but won't tell me where I am if I'm lost unless I have my iPhone(… I'll never understand that one!). Would it have been that hard to add a small screen?
Some day they may all come together in a light weight "do-it-all" device but I suspect it's marketing that is keeping them apart not technology… which is bad news for light weight backpackers.
I most often carry a 2.4 oz GPS (that weight includes two AAA batteries) and I leave it on when I'm walking (collecting tracks). It will run for about 3 days on a set of batteries however the batteries weigh less than half an ounce for the pair, so spares are not a big deal.
The irony is that my GPS is left on in my pack and I never look at it. I look at my map all the time. So why carry the GPS… because I like looking at the tracks when I return and I match my photos to my tracks. So basically, it's a toy that I like to take with me on my trips. I'm OK with that because it extends my enjoyment of my trip to days after I'm finished the hike (same reason I carry a camera and take pictures).
It's all a compromise and you just have to rationalize need vs weight vs enjoyment for whatever you carry.