I voted in the category of "other".

In my case, I don't currently consider cellphones as necessary.
I do, however, think they are useful to have.

When not on my bicycle, I carry my cellphone either in my pocket or in a case which hangs from my belt. I often use it while away from my apartment, summoning taxicabs where public telephones are few and far between, and other reasons. When bicycling, I carry a cellphone either in my trunk bag or in the pocket of my cycling jersey. My rides have been uninterupted by it most of the time. When I do hear it ring, I pull over to the side of the road to take the call. I also have it available in case of emergency.

EXAMPLE: I have epilepsy which is controlled by a number of medications. Although the medication levels in my blood are strictly monitored, occaisional "breakthrough seizures" occurr once in a great while. I haven't had a seizure in years. On occaisions when I 've experienced "Petit Mal" or partial complex seizures coming on, I've usually been able to pull off the road, dismount, and sit down before using the cellphone to summon an ambulance. At other times, I've experienced Grand Mal or "Big Bad" epileptic seizures, I was forced to ditch and had to wait until I regained consciousness. Yes, I wear a helmet whenever I'm out riding. If I should find anyone in need of help, I would use my cellphone to contact paramedics or police.

I was the last person in family to get a cellphone