Recently Apple released a special case for iPhone 4 called ‘Bumper’ case. This case can protect the iPhone 4, while at the same time it could avoid signal problem.
However, if dislike wearing case to your iPhone 4 and want a quick solution to solve signal problem, here is a beautiful-made Band-Aid called Antenn-aid to improve your iPhone 4 signal performance!
Just stick this Antenn-aid to the lower left corner of your iPhone 4 and you shall see a positive feedback in the signal quality. This Band-aid looking Antenn-aid is available in several nice looking colors and it’s available for $4.99 for a pack of 6 antenn-aids.