Voicemail app that doesn't require carrier voicemail

I'm looking for a voicemail app that will answer my phone after a configurable number of rings and route the caller to voicemail stored on the Android device. I don't have voicemail with my carrier. I'm not interested in features of Google Voice because it seems to piggyback on real voicemail and also I don't want to port my phone number to another service if indeed that is required. (Note: I remember doing something similar on a PC desktop years ago when the phone line was hooked into the modem, the computer would act as voicemail.)