New day, new tweak in Cydia, and as far as you can tell from the title , you can set up your home button to open up any app you want or any webpage on duble tap. If you use QuickBoard, you might wanna decide which one you want to use, because as you know Quickboard is using double tap of the homebutton to be accessed. Or you can set QuickBoard to be accessed when you double tap on the StatusBar of your iPhone.
As i said above you can get this tweak from Cydia, and you might have to add the TouchMania Source : http://cydia.touch-mania.com/. Once the app is installed you need to load the Settings app and scroll all the way down untill you see a section called Custom HomeButton. There you need to turn ON this tweak, and set which function you want it to run when u double tap the homebutton on your iPhone or iTouch. You can set it up so when you double tap the homebutton it will open either a default iPhone / iTouch app , an AppStore app , a Cydia App or a Website. You can choose from the list of apps and website, or you can add a custom one. Your choice.