I am currently not developing an Android app, but even an interested user like myself can learn useful stuff from Nikolay Elenkov’s blog. Nikolay is from Bulgaria, but he writes in English as if it were his native language. His knowledge is condensed in a book, titled “Android Security Internals: An In-Depth Guide to Android’s Security Architecture“. The book is available electronically as well as in print.
His Google+ feed contains interesting bits as well, by the way. I don’t know if I will need any of the details explained by Nikolay anytime soon, but with this post I’ll be soon to find him quickly when needed.