This device is far less unreasonable than it seems.
LFDs (lateral flow devices - the paper strip used in this test) are simple in theory, but get a human being involved and what *should* be simple and clear becomes variable, vague and uncertain. In most cases where there's a pregnancy then a nice clear line will develop, but sometimes it can be faint, or sometimes people will see a positive reaction where there isn't one. Attaching a simple detector with a pre-determined threshold (possibly matched to the batch of components used to create the LFD) will remove the uncontrolled human factor and will provide a more reliable result.
FWIW I've had a little input into developing LFDs for other uses, and they can be a challenge for everyone to read. Lab coat obviously, because who'd risk spilling someone else's wee on their clothes?