I made a pair of matching shock collars for my wives. Only one likes to wear it all the time, and she is very much a dog girl. I usually wake up last in the morning, and really like being able to summon my coffee by remote (using the vibration function instead of the shock function. I am nice).

For a pair of pets, I endorse the Dogtra IQ Plus shock collar. Its controller has a slider on the front to switch between two synched collars. I selected it due to an online recommendation and do not have experience with other shock collars, but it has performed as well as I hoped.