I know a physicist who works in this area, and I asked him about this. I'm just an engineer, so he knows to translate into English. This is what I heard. If any physicists want to weigh in and correct me, please do.
There are different types of "atomic" clocks. The one in my bathroom doesn't measure atomic oscillations, it is just a radio receiver, picking up the transmission from NIST in Colorado . Their time base is maintained by "an ensemble of cesium beam and hydrogen maser atomic clocks" .
I think that these NIST clocks, as well as the ones on satellites (GPS, GNSS, etc.), operate by measuring the oscillations of atoms. This is accomplished by exciting the electrons to higher energy states, with lasers or masers.
The energies required to change states in the nucleus are generally much higher than those for electron states. Recently, they have found a nuclear energy state transition that can be excited by a UV laser. Because these states in the nucleus are much more stable, and less susceptible to effects from neighboring atoms than the electron states, the measurements will be much more accurate.
And I agree with Powercntrl. Atomic power for all our battery operated devices would be a great thing.
There are bugs and then there are bugs. And then there are bugs. -- Karl Lehenbauer