Mine are 13 and 15. Yes. My oldest would even sleep in and meet us later at whatever park we were in. When I was a kid we'd go on school field trips to theme parks and around age 10 were let out on our own without cell phones, and just the instruction to be a X location at X time.
If a kid has a phone or a watch and can follow instructions, and is responsible/trustworthy (only you know what your kids are capable of) I see no problem with it.
In my opinion, kids need an opportunity to figure things out for themselves sometimes. I coach Odyssey of the Mind (a creative problem solving competition team), and while most of my kids have been with me since elementary school, each year I get a couple of new ones with no experience. The point of the team is that the students do EVERYTHING themselves: write their script, build all sets/robotics/whatever (including using tools if necessary - with supervision), create their own costumes, etc. Often, kids new to the group have zero idea how to do anything on their own or make their own decisions. They have no experience doing things without being told exactly what to do, b/c in school or at home they have someone directing their every move. It is challenging to coach those kids, but they eventually learn, and their confidence grows by leaps and bounds.