It's been there for a while. I've been typing "timer 15 min" in my Chrome quicksearch for well over a year, according to my browsing history. They just never really did much fanfare about it - this came around the time where Wolfram|alpha was an online sensation because of its smart parsing, IIRC.
Yeah this has definitely been around quite a while. I still find it much easier to just open a timer app on my phone. It provides a much nicer UI for selecting a time (scroll wheel) as opposed to typing it. This is handy when at a computer but I could see myself accidentally closing the tab/window and losing my timer.
I like the look of steep.it. Not that steep tea that but it's a nice idea and is more colourful than Google.