I did this recently in an application. There was so little "code" to it that there is barely anything to post. I did it as such:
Created a UIImageView (about 50 px high), and laid it out at the bottom of the screen. I filled it with a tab-bar look-alike image - i.e. some sort of grey gradient. I probably subclassed UIImageView - but you don't even have to do that.
I drew a bunch of buttons/icons - 37x37 each.
I placed a bunch of UIButtons in the "tab bar" - and made them "Custom" views, with the buttons/icons I had created.
I simply used the touchUpInside methods to make them do stuff.
When I needed to get fancy - I'd attach the buttons to my code via and IBOutlet, so I could "disable" them - and I'd draw a greyish "disabled state" image for them.
