Personally I'd not ever really need the last call as its just as easy to go click the phone button on the bottom to take me right there (if that's how you set up atakephone to begin with of course)
Whatever you end up making, PLEASE consdier some of the newer devices have larger screens and 4 icons across might be a bit larger than we need. (perhaps an option to scale?). I've tried quite a few widgets, that do exactly as you seem to be heading, and honestly they just don't work as good as your Ibar. The scrolling itself seems to be my biggest gripe, as it's a lot faster than clicking an icon.. especially when it's so easy to misclick.
Personally I'd be happy with a Vertical bar even that allowed scrolling so long as it was only 1 across. Similar to the HTC Sense "People" widget, but allowed for more than 3 pics at a time and didn't take up half the screen
I know vertical scrolling is allowed in several launchers now (ADW and Launcher Pro)
Also one minor issue that is driving me nutts... I don't know if something changed or if I never had the sound on but I HATE the default selection sound in takephone. The dialing sound is great but anything else such as moving from favortes to dial, has an awful "thwap" sound. I would like to request either the ability to change the sound (via custom ringtone/sound file) or at least provide some alternates that are a bit more ear friendly. Again it's a minor issue and has no functionality problems, but because of it i've had to turn off the sound entirely.