You can set a quick timer by typing, "set timer X minutes" into Google. Once you hit enter, the timer will count down, and then sound off when the time expires with an obnoxious, possibly never ending tone. If a countdown doesn’t do it for you, then you can also use the command, "set timer for X time." It’s a pretty simple, but effective way to create an alarm without installing any special software.
For more fun, try this on your Android in Google Now and then in Chrome. I like talking to it!