It's a nice idea but when i've looked into this, the monthly cost plus the excess puts the cost into 3 figures after a few months. Then there's the hoops you have to jump through to claim and ofcourse the get outs. I'd sooner take the risk than spend £100+ anyway plus have all that hassle. I suppose if you clain within 2-3 months it's worth it but if you were to claim after 12-18 months then the amount that you have paid in premiums plus the excess to far too big a chunk of the phones current value once it's 12-18 months old.
I insured my £400 phone for £50 for a year with a £50 excess.