Phone trouble?

Don't you hate it when you get into an area where the signal strength is weak for your mobile?
I discovered small so called signal boosters while I was trawling through E-Bay the other day.

These consist of a small waveguide which sticks inside the phone . 
The pack they come in suggests that they cost $19.95, but you can find multiples of them on E-Bay for around a pound.
I stuck one in all the family's phones and, so far, results seem promising.
If you think these may help, have a quick search on E-Bay.