Microsoft keeps buying some of the best third-party apps on iOS and Android. After scooping up Acompli (quickly rebranded to Outlook) and then calendar app Sunrise, the company has now apparently set its sights on Wunderlist. The Wall Street Journal reports that Microsoft has agreed to acquire 6Wunderkinder GmbH, the Germany-based startup that created and develops Wunderlist, for a price somewhere between $100 million and $200 million. The deal hasn't yet been finalized and the Journal is sourcing "a person familiar with the matter" for its report; Wunderlist declined to comment on the matter.

The Wunderlist buy represents Microsoft's latest move to boost its mobile presence and cover all bases around productivity software; Acompli checked off email, Sunrise was calendars, and Wunderlist gets the company a well-regarded to-do app. Wunderlist has earned favorable reviews among Android, iOS, and Windows Phone users. (Desktop versions also exist for Windows and OS X.) Back in March the company launched redesigned apps with smarter task management. Without any direct confirmation from Microsoft or Wunderlist, it's too soon to know Microsoft's plans for the app. Acompli was quickly folded into the company's product portfolio, while Sunrise has so far remained more independent and retained its original branding.

Update June 1st 1:55PM ET: The Wall Street Journal originally reported Microsoft's purchase of 6Wunderkinder GmbH was for between $1 million and $2 million before correcting the estimate to be between $100 million and $200 million. Our article has been updated to reflect the new figure.