suggest options for handling anonymous calls on VoIP

At the moment on a VoIP line I can specify anonymous call rejection, and can record a custom message. I can think of a couple of other ways that anonymous calls could be handled:

1/. Play the message, and then drop directly to voicemail. OK, so doesn't solve all the problems with ACR, but it means that friends and family who withhold their number get a chance to leave a message and I'll call them back. If someone doesn't want to leave their number, we're still a bit stuck though...

2/. Play the message, and then allow anonymous callers the chance to enter a PIN via DTMF. If the PIN matches the stored one, let the call through. This enables me to tell friends, family, and various parts of the NHS that they need to enter this PIN (which I could change on a regular basis).


I'd have to make it clear on my custom message what anonymous callers need to do.

Oh, a question - does anonymous call reject affect inbound SMS texts ? Could I tell anonymous callers to send me a text ?