My phone (Panasonic) can assign different rings to different categories of caller numbers. I have one ring tone for family, one for friends, one for medical contacts (surgery, dentist, physio) and so on, so if anyone phones who is not one of the regulars, it is obvious from the sound of the ringtone.
And caller id is worth the very small monthly cost. It shows the number of the caller, and the name if they are in your phone-book list. It doesn't work for withheld numbers, or for "out of area" overseas callers, but it does identify a lot of callers.