I found this plugin today and it works great for what I want it to do, though I made a couple small changes to my local copy:
- I commented out the time variable for the cookie. Rather have it expire at the end of a session than in a whole year. :) This might be useful as an option.
- I commented out the admin message when maintenance mode is turned on. I can see why this is a good idea generally, but since I'm using the plugin a little differently, it was a bit annoying.
What I did was create a static HTML page for the maintenance page - a "coming soon" page. Then I created a token and sent it to myself that I can use to bypass the maintenance page. I created a subfolder and put a php redirect in there to the bypass link. Now I can give the client a yoursite.com/preview link that lets them view the site for one browser session. When they close the browser, their next visit to the home page will be the maintenance page again. This alleviates some confusion, and allows them to see the landing page everyone else sees when they want to. Plus I don't have to keep track of any individual allowed IP addresses and so forth, though that feature is bound to be handy for some.
I disabled the maintenance mode message in admin just for convenience, because it will be in "maintenance" for several months (this is a new site).
My use may be somewhat novel which is why I'm posting this. The plugin works well though in my case even without any modifications.