The prepaid cell phone is exactly what I do and I LOVE it!!!
I have a cheap but adequate phone that I got for free from a friend when he upgraded.
I have a prepaid account with T-Mobile. I pay $100 and get 1000 minutes that do not expire for one year (so 10 cents a minute). No need to add more points every month, and if I have leftovers at the end of the year they roll over into the next year when I add $100 more to my account.
I carry the phone always but use it only in emergencies, for an easy contact when Denali is at school or with a sitter, for finding friends when we meet up, for traveling, and for "quickie calls" ("Hi honey, I'm at the store: what do you want for dinner?"). I NEVER chat on it, and I let people know that I don't really use the phone for general conversation.
Last year I used 950 minutes, so my whole cell phone bill for the year came to less than $100. I had all the benefits of using a cell phone without a monthly payment or a contract.