We've written an Android library just for that.
https://github.com/EverythingMe/webp-android
webp-android is a library we use at EverythingMe since we love webp. We use it to save bandwidth as well as shrinking our APK sizes.
webp-android is an adaptation of chromium's webp decoder, and an addition of a JNI wrapper to easily use it it in your java code.
It's also easy to load webp images from xml to an ImageView (with the included WebpImageView) like so:
