I have no idea how useful this little web-app may actually turn out to be, but it's definitely a neat idea (and I wrote all of this in it too!). "The Most Dangerous Writing App" is certainly an odd one: keep writing in the completely streamlined text entry box for the allotted time limit (you set this yourself) or else "die". Death, in this case, doesn't refer to some chain-mail-esque curse, but the threat that if you stop writing for longer than ~5 seconds (total time unknown, I conducted a few simple tests but nothing too rigorous) the screen and box begin to fade, a red haze descends and then, ultimately, the "time's up" message hits. At this point, it isn't just game over... it's message gone. Your entire piece of text (all of it) gets deleted, leaving you with a red screen, a red face and nothing to show for the effort.
As a result, I'm not convinced I'd ever want to try a time limit of longer than 5 minutes (which is what I've been experimenting with), just in case something went wrong. I'm also not sure what counts as "typing"; I went to correct typos and found it fading out whilst I was still hitting backspace, which was unnerving. Still, it definitely makes you stay focused, which is no bad thing. If that results in greater productivity then perfect, though I definitely felt the stress rising towards the end as the timer ticked down, my mind largely becoming clouded with thoughts of "this would be awful if it disappeared now".
That said, once the timer has run down the option to Save or Restart becomes available and the risk of losing everything goes away, so I guess it's probably a very good way of "getting in the zone". At any rate, definitely worth a look, even if it's just for some quick writing challenges or to get thoughts out without any formatting worries. Will likely try it out a few more times in the future!