Lightbulb Idea For Application Against Scam / Direct Marketing

Sometimes I get calls from private numbers or numbers I don't recognize. I don't wan't to bother answering because it could suck me into unpleasant and annoying conversation with snake oil salesmen, scammers or someone I don't want to talk to.

I was thinking of application which could allow me to:

1. Identify questionable number using central database of known numbers if possible
2. Present me with following options:

a) Send to my carrier's voicemail to leave message
b) Send to 3d party voicemail with my custom greeting message recorded asking caller to identify himself and leave number to call back to

It would be great to set by default unfamiliar and private numbers to be transferred to one of above options of my choosing

Sometimes there are legit calls coming from unknown and private numbers that I miss. That's why the idea for application that could do above.

What are your thoughts about this? Is this feasible?