Hi,
Yes you can keep your computer off. Auction Sniper does all the work for you, that's the best part. You can set a snipe days in advance and go on with your life. We'll make sure the bid is placed. (And if it makes feel better, we succesfully place thousands of snipes a day!)
As for Snipe-It-Now, this feature allows you to snipe right from an eBay item page. You click the button on your links toolbar, and a new window will appear allowing you to enter your snipe information. Here is the Snipe-It-Now homepage:
http://www.auctionsniper.com/?p=snipeit
Adam R.
Auction Sniper Support