Things They Should Invent: voicemail that automatically deletes blank messages

Every day I come home to three or four blank voicemail messages from telemarketing machines gone amok. I wish my voicemail could just detect that the message is blank and delete it, so I don't have to go log into my voicemail and go through and delete the messages myself. Even though I know to press 33 to skip to the end, it's still an annoyance.