Underground radio type fences

Recently moved from a rural home to a suburban home about 1 year ago. My 2
cats previously had an indoor-outdoor lifestyle. Ever since the move they've
both been bored and depressed while living indoors only. One of them (a 5
year old) is now unhealthily bony. So I'd like to enable them to go outside,
at least while I'm also outside with them. However, they must stay confined
to the rear yard. When we lived in the rural area, a fence wasn't necessary
as they never wandered outside the expansive property boundaries, and if
they weren't in close proximity to the house, they would return for dinner
via my loud whistle call.

If any of you have any experience with those buried cable fence systems
(invisible; utilizing an electronic cat collar), please remark. I'd be
willing to obtain a system if it sounds like it could be reliable.