Which is 47 mm x 30 mm x 15 mm vs the Mictrack's 46mm x 41mm x 16mm - and that 11 extra mm would make it not work on a collar. Fitbark does have Bluetooth.
I've got a really wandery cat whose range is about 1-1.5km in any direction from the house. We try to keep her within 0.5km as much as possible. If we didn't manage her location fairly actively, she'd probably wander farther.
The catch is that my cat's use case (being mostly outdoors, mostly out of Bluetooth range, and mostly draining power) doesn't match the engineering design model of a dog who's with you most of the time and might escape on occasion. They gave me a more power-conserving build, though.
The one anomaly here is one I've noticed with Pokémon Go as well: "rounding" locations to be at the street even when the cat isn't even within BT range of the street. (For privacy reasons in PoGo's case, after multiple lawsuits.) The one time this is particularly annoying is when our fuzzball is hunting lizards in the local schoolyard at night, and the tracker says she's on the street next to the schoolyard, but she's somewhere in the middle of it.
In practice, that means I know where my little darling was 10 minutes ago, rounded to the nearest street, and use a Bluetooth tracking app to narrow it down further. Naturally, a good third of the time, she's within BT range and just Not Interested™ in moving from wherever she happens to be. (We try to keep her fed on a regular schedule to reduce wildlife consumption.)
We're going to try FindMyCat on the other cat (who currently doesn't have a tracker) and see how that goes. He spends more time at home.
(Analogously, If software engineers only worked for perfect companies, companies wouldn’t have software engineers.)