Active RFID tags have significantly bigger range, up to 12 meteres (last time I researched this topic). They shouldn’t be too big either, but range(antenna) and battery life are strictly linked to size of the tag. Wholesale prices are a fraction of a dollar for 1 tag, but production costs/assembly costs would need to included too…
I don’t think that active rfid tags will be strong enough for bigger houses and false positive (phone in bedroom, wallet downstairs) situations can happen.
That being said, NFC in phones is not the same as UHF RFID, so I’m not sure how active or passive rfid tag could be read by phone. Can it be solved without adding 3rd device to be a link between phone and card?
Maybe we can have some sort of tracker (any technology) with nice battery in a form of keyring attached to card? Can cards have holes? Contactless wouldn’t be affected and you put only half of the card in POS terminals - those can use card with tracker attached. Only ATMs would require user to detach tracker dongle, but it would still need to be nice/quick to attach/detach tracker. Card would still fit well in wallets in most cases if tracker dongle has good shape + not very big.