But it's interesting, that it's so difficult to find a good online-diary. Diary.com is the best so far, but the Android app is horrible, while the website on the desktop is quite okay.
Penzu.com is not usable for free. The mobile app doesn't even work without a pro account, and the features are really cut down too much even for free.
GeoDiary2 on Android is awesome. But no real sync, no web-based centralization. So, like I mentioned above, it's not usable for me. Using Tumblr.com or another blogging service could be an alternative, but password protection alone is not good enough. Without encryption, it's always possible that a search engine can find and index data.
So for now, the search goes on, and the wait for a better Android app for diary.com