Oooh! Is "Lo-Jack" the one that shuts the car down and provides a GPS signal? That would be much better than a microchip. ...but I am LOVING the suggestion of Instant Magnetic Return! (maybe we could develop something like that for car keys, too)
Dave, we have been brain-storming about building an outdoor kitty enclosure and turning our patio into a Florida Room with screens.
We may have a solution to your escapee problem:
We discussed how flimsy screens are, as we've found to the detriment of our home windows, and have been thinking about ways to protect both the integrity of the screens and provide a secure barrier to keep cats in, other things out and still allow for maximum air-flow.
What we've decided on is adding a heavier barricade to the lower part of the enclosures. Something inexpensive like panels of wire 'hardware cloth' securely stapled to a wood frame or even small-hole wire/bar sections like those used for dog-crates securely fastened around the structure.
Could you install something like that?