I think, based on experience having worked in Baggage-related projects for a few years, that these devices will be next to useless in terms of finding bags, for a number of reasons. Firstly, many Baggage Handling Systems - such as T5 - are buried deep under a lot of concrete and steel. Trials using radio-emitting beacons have proved that, unless there are repeaters of some sort nearby, their range is very limited.

Then there is a fundamental difference between bags being "lost" and bags being "short-shipped". The latter is what happens in the majority of cases when you arrive at destination and bag isn't there. The airline has visibility of where the bag is; they're just pretty rubbish at telling people (and their own employees). Out of a 1,000,000 bags that fly on a good airline, approximately 5,000 will not make it to their destination at the same time as their owner. Out of these 5,000, between 4,900 and 4,950 are bags that got stuck in the system: most will have missed their connection, some actually got stuck on some conveyor, some had contents that required inspection and then there was no time to load them, some were bags left behind when the plane was full and yadda yadda yadda. The key here is the airline has information on their whereabouts, usually quite accurate. It just has varying degrees of success in sharing that info with its people and its customers, as well as getting that bag on its way to where it needs to be.

A bag in its journey through T5 gets scanned tens, sometimes hundreds, of times. So they're never 'lost'. A bag tracker, in this case, isn't really useful. We did some trials and, besides those that simply didn't work or reported the bag as being on the runway while it was on an arrivals belt in T5, even if it said "hey, the bag is in this corner of T5"... It wouldn't really say anything as there could be up to 5 levels of belt conveyors, trays and other machinery stacked one on top of another in that place. And I can simply access HAL's tools and see where the bag was scanned last, knowing that it'll be nearby.

A minuscule proportion (as I said, roughly between 100 and 50 bags per 1,000,000) are bags that simply disappear (their tag is ripped off and they have no recognisable traits, or they are nicked, or the bag courier leaves it on the kerb and so on). In this case, no one at the airline has the foggiest about the bag's whereabouts. This is the situation where a bag tracker would come handy but... will it still be charged? Will it be in range? Will it be accurate?