I just discovered this app in the App Store. Not certain if it's available outside the UK but a great range of channels available including all the UK terrestrial channels.
It's an iPhone sized app but when run at x2 the picture is absolutely fine. EDIT: I have just checked the web version and it looks like they have removed the adult channels from all versions which is great news for those with kids.
I've only watched a few minutes so not sure yet if it's time limited or completely free but the app is free to download.