Apple is hosting a big event in San Francisco today to show off what is widely expected to be the debut of its first major innovation since the iPad: the Apple Watch. You can follow our live blog here.

We've already sort of seen the watch, of course, first at the latest iPhone event in the fall, and then again and again through the eyes of Apple executives such as Tim Cook and Jony Ive in media interviews. But this will be the device's big, center-stage debut.

Here are some key things to look for when the Apple Watch grabs its spotlight:

Battery life: This is a very important question. There have already been reports that Apple's Watch will have a lousy battery life, with as little as 2-4 hours of active use. If the watch becomes a product that you have to charge in the middle of the day, that will make it far less appealing to the average person. You want the Apple Watch to make your life more convenient. You'll want something that charges daily, at the very least, and ideally over at least two days. Most smartwatches pass that daily test, though Pebble's smartwatches -- which have an e-paper display similar to the Amazon Kindle -- can last up to seven days on one charge.

Battery life becomes even more important over time as Apple undoubtedly adds functions to its watches, particularly if you're going to make it the key to your home and the main way that you pay for things. The battery doesn't ever go out on your old-fashioned wallet, after all. Ditto for your house key.

Price: Apple has already revealed that the watch starts at $349, but hasn't gone into any detail about the prices of the two more expensive versions. Estimates for the most top-line watch, wrapped in 18-karat gold range from about $1,000 to a whopping $10,000.

But most people will probably be looking at the sport watch -- the aforementioned $350 model -- or the middle tier if they don't want something that looks like a fitness band. That price point will matter a lot, and will help determine whether Apple's looking at the Watch as a tech accessory or a piece of fashion in its own right.

When Apple announced the stock last fall, watchmakers' stocks sank across the board. And subsequent earnings reports from mid-tier watch companies such as Fossil and Movado show how vulnerable the sub-$1000 market really is.

Features: Maybe it should go without saying that features can make or break the Apple Watch. But with so many news reports and columns predicting how the device will compete with the fashion industry, sometimes we forget the basics of the tech itself.

And there's a lot of technology to discuss. Apple is obviously a big name. But shoppers will be able to buy fitness bands from FitBit and Jawbone for a lot less. And if the Apple Watch can't execute other tech beyond a step-counter and heart rate monitor, it will be a hard sell to anyone outside of the company's existing fanbase.

Apple is smart, though, and likely has a lot of tricks up its sleeve -- Cook has said he's come to rely on his Watch, which is a pretty big statement to make -- but it will really have to sell users with watch functions that they will struggle to get anywhere else.

(Graphic by Darla Cameron and Kevin Uhrmacher.)