Nothing precludes you from upping the TTL after the change. Traditionally DNS admins progressively drop the TTL prior to a change to reduce the time an RRSet is in flux (so if your TTL is N, N + 1 seconds prior you drop…
DNS Push Notifications[1] could be tacked on to resolvers and clients. 1: https://tools.ietf.org/html/draft-ietf-dnssd-push
Is there anything like this that can act as gadget devices for more than one host? (So I can plug it in to 4 different PCs or the like)
Nothing precludes you from upping the TTL after the change. Traditionally DNS admins progressively drop the TTL prior to a change to reduce the time an RRSet is in flux (so if your TTL is N, N + 1 seconds prior you drop…
DNS Push Notifications[1] could be tacked on to resolvers and clients. 1: https://tools.ietf.org/html/draft-ietf-dnssd-push
Is there anything like this that can act as gadget devices for more than one host? (So I can plug it in to 4 different PCs or the like)