nice work! wish i could code GUIs too. ^^ as i can see you are using the current time as qrand()-seed... looks like we had the same idea xD
i haven't the time to look at all your files... but is the random file only set when the user opens your app and clicks on the button or is it set automatically each time the phone starts up/ shuts down? (if not that would be a suggestion worth implementing ^^)
also i don't know if your program shows the random selection to the user after clicking on the button but if it does so then the surprise wouldn't be there on startup (because the user already knows which video will show up... so i would like the "kinder surprise"-style more - not knowing what you'll get *g*)