I use Callcentric VOIP for my landline. They have a fantastic feature that has eliminated marketing robocalls. It works like this: unless the caller is in my contacts, the call is answered by Callcentric's own robot, which asks the caller to press a digit to be connected. Real human callers press the number, but robocallers assume it's voicemail and hang up. The vast majority of telemarketers use robocallers, so this has been extremely effective in getting rid of spam calls. Is there an Android app with this functionality? All the call blockers I can find are just some variant of whitelists and blacklists. That just isn't good enough!