I have the BIG Casio, altimeter, solar, atomic, elec compass, barometer,tide and moon, so many buttons I have to carry the manual in a backpack. But I love it when hiking or even driving into the mountains and wondering how high I am (no jokes here).

Seriously, it's huge, but completely self contained and accurate, and if exposed to sun regularly, in theory will never need batteries.

I also have a Citizen eco-drive diver, same solar capacity, not so humongous.