In a past life I sold truck systems like the one you describe. These could monitor 24 tyres to an accuracy of about 0.1 PSI and would bring on a yellow light when the pressure was down by about 2%.
We also did ABS systems that can monitor each axle end and bring on the light when one wheel speeded up by about 5%.
With both you get the driver to react before the tyre is damaged, which at £200 plus a tyre, maybe £10000 if they close a motorway lane to fix a blowout and millions if your petrol tanker crashes, it's well worth it. In the direct system you get single pressures without the driver spending maybe 30 minutes checking. Indirect is a tiny bit of software in the ABS, so is almost free.
With a bike I can see the advantages if they are OEM fitted. Retrofit, does it really take that long to take two pressures? For say a police bike I can see it'd pay for itself in tyres and the safety's for free, but on a private bike?
I now sell gauges
A pencil type gauge has an o-ring which wears, sticks and generally misbehaves. They are highly innacurate but repeatable if used by the same person. A bourdon type gauge (round) is typically accurate to 1% and should be repeatable, but will go out of calibration if you carry them about and vibrate the tube. A digital gauge is both reliable, accurate and repeatable, but best of all doesn't go out of calibration so long as the battery is good and it is allowed to zero to the atmosphere on start up. I'd always go digital on a tyre gauge to carry with maybe a bourdon in the garage if the odd half PSI worries you.