I've used the Joykatz walking jackets since 2003...I love them! http://joykatz.net/walking_jackets.htm
I have found that properly fitted (the right size and they need to be firmly wrapped around their middle with no wiggle room) they are very secure. I've had to suspend a kitty more than once to bring to safety (aggressive dogs etc) and never had them wriggle out nor break out of the jacket.
There are other designs out there that are nice, Arden Morley of Camelottaspots makes some in some really cool fabric choices... but I keep going back to the Joykatz ones for the fit. They are a little curved in the cut around the neck that seems to sit better.
I haven't used any other than the JoyKatz jackets but they are definitely great. I also like that they are reversible and by request you can get them with two different fabrics. No self respecting cat should need to be seen in the same jacket all the time. Definitely have a collection of them and it looks like I'll need a couple more with a pending new kitten and Chongo getting ready to outgrow his current jacket.