Hopefully it's just a matter of time before we can replace owner-pleasing dogs with something that won't give a false positive in order to get a pat on the head and a treat.
Cops will only buy and use them if it gives them the results they want. It's the same reason the field drug tests are designed to give false positives[1], and why body cameras can be turned off at-will and are advertised to police departments as devices that keep cops safe from the lying public.
That's assuming they keep up on any necessary calibration and maintenance, as well as proper training. Just seems like another potential avenue for abuse and/or false positives.
Calibration and maintenance of electronic devices is much more transparent. Defense attorneys successfully challenge breathalyzers and similar instruments all the time.
One reason dogs are unlikely to be replaced by a device is precisely because 1) dogs are opaque instruments not readily susceptible to critical analysis, and 2) have long been given the benefit of a doubt--much like cops' famed mind-reading faculties. From the perspective of the police, it's a don't break what isn't broken situation.
Hopefully it's just a matter of time before we can replace owner-pleasing dogs with something that won't give a false positive in order to get a pat on the head and a treat.