I installed the Sprint OTA KitKat update yesterday and the fetch continues to work... sort of. I've found that if I turn the fetch off I have to go in and find it again and pair again.
I also noticed and downloaded the HTC Fetch app in the app store.
It has a nicer interface and apparently a couple of additional features (including the ability to connect to other BT 4 devices)
It apparently connects differently as you can run it without it being paired in regular BT settings and it doesn't retain the annoying Fetch icon in the notification area. BUT, since it no longer shows as a BT device, the Pebble Unlocker app that I use to simulate 'trusted device' doesn't see it and doesn't keep the phone unlocked.
I'm hoping there will be some interest in the developer community because I think there are some enhancements that can and should be made to either or both of the apps.
For one, I'd like to be able to disable change the tone or somehow further delay the alarms that go off when out of range. I do that far too often. However, when that feature is disabled, it also disconnects the BT connection and as above defeats the trusted device functionality mentioned above.
I mostly want to use it so my phone is secure if I'm not nearby and occasionally use the separation alarm feature if I am in a situation where one or the other might be left behind.