is it possible (trough jailbreaking ?) to lock an ipad into single app modus so when it starts it just starts 1 app and it\'s impossible to see the springboard homescreen?
Yes, you could write a MobileSubstrate tweak that launches the app when SpringBoard starts. Then you'd also have to override the function of the home button. Shouldn't be too hard. If you don't know how to write MobileSubstrate tweaks, look into theos, it makes it really easy.