Its a good idea, but surely their pron to damage with other trades using the scaffold. A scaff tag can be replaced if damaged and the insert re-inserted with ease. If this device gets damaged what the cost of repair, you then have to put a normal scaff-tag in its place till its repaired.
You've also got to carry a tablet or phone round with you on site all day, surely a pen is quicker to sign a tag, compared to uploading the info then updating it, im sorry but i bet i could update a tag by pen quicker than by phone. Again its a good idea but it seems to expensive to have on sites.