You need to be a subscriber to pay TV on cable or telco to see everything:
NBCOlympics.com will live stream every single event (they'll even be on YouTube, and in the UK the BBC has its own plans) for the first time ever including streams of each of its channels, encompassing 3,500 total hours and the awarding of all 302 medals. The bad news is that if you're not a cable subscriber, many of those hours will not be available to you, and even if you are, you're looking at a (likely convoluted) authentication sign-in process.
Also new for the internet are multiple streams for the same event, so for example, viewers can select a particular gymnastics apparatus or track and field event at will.
On mobile devices, NBC also has plans for two different apps on phones and tablets, with one that brings live video streams and another with highlight clips. It didn't specify what platforms they would be available for, but we'd assume the usual suspects (iOS, Android) will be first up.
For the full breakdown of all 5,535 hours of coverage across NBC, MSNBC, CNBC, Bravo, Telemundo and everything else check out the press release after the break