I have been getting so many promo emails for Blink XT that I decided to whip up my own. At 129.00 USD, CDN 170.00!, I decided to spend 4.00 at Canadian Tire and buy a glass container with a water tight snap on lid. 4 dollops of silicon, some knife cuts and voila. I glued a speaker swivel on the back as a mounting bracket.
The black tape is temp as I found the plastic front cover acted a bit too much like a light pipe; when the flash would go off the lens would get a bit of white wash.
Creativity is good. 
One point to consider: if “watertight” also means airtight then you should create some venting as well. Battery devices outgas over time which can create a fire hazard if there’s no vent available.
Definitely not water tight anymore 
I wanted it to breath with the temp changes. The holes are cut tightly but there is a small, press fit gap.
Basically it’s under the eve and if water hits the enclosure it cant be forced or wicked in around the lid or base.
