How to notice a phone is ringing when left in a bag?

I always carry my cellphone on me on vibrate, because I'm male and this works with my wardrobe. Many women I know carry the phone in their purse or other bag, and they often miss calls, not noticing the phone is ringing. At the same time, they don't want to have the ringer volume set very high, so that it's a nuisance to others. How can they notice the phone is ringing, when it is not on their person, and not loud?