An app called Dark Sky came out, powered by Forecast.io. Several months ago they rebranded the service to DarkSky.net which continues to power the Dark Sky app, along with other 3rd party apps like Forecast Bar.

Nope, forecast.io became darksky.net, some months ago. Also, WRT your other comment, I live in Istanbul and find it very accurate, whenever I see that it shows some precipitation I take the umbrella with me, and thus I've spent the last two years way more drier.