some insurance is worth while but alot of it is just easy cash for insurance companies, for instance the electrical stores like comet who try and flog you extended cover etc.
if your clumsy then of course its worth while or if you're dishonest then its still beneficial, as i fall into neither catergory i don't tend to take them out.
i've had a mobile phones since 2000, and only ever had 1 break on me in 12 years, so mob insurance seems surplus to requirement. but like dan says if your out and about doing a physical job the risk is higher.
tyre insurance is a funny one; in 13 years of driving i've had 3 punctures, and all of which were repairable at a cost of £30 each; so i've spent £90 in 13 years, also i don't liek the idea of changing just 1 tyre, so at least with a repair the tread depths will match across the axle.