Most instant meeting tools require a download. Also, most of those services are chock full of security holes or are bloated. Mine doesn't and works with all browsers and mobile devices. It's based on Kopana Meet which you can learn about if you want.
Cost is $2/month/registered user and is billed monthly. Includes access to my TURN server. If you don't know what that is, just know it's what makes it work. I don't charge for access to TURN as long as you aren't getting crazy.