My cellphone is in my pocket at all times. It reminds me to take my medication, it's my alarm clock, it reminds me that it's time to take my grandson to work, and most importantly it acts as an emergency contact device.
11 years ago I slipped on the stairs and went sledding down the whole length on my behind. Broke my tailbone and was paralyzed for several minutes. Cellphone was in my purse, I think -- definitely not on me. If it was I could have called 911, or one of my daughters, or someone for help. As it is, I just sat/laid there and waited for DH to come home from church.