Saiy - An Open Source Voice Command Assistant for Android
This is a fully open source alternative to Siri or Google's Assistant. Although it uses the Google voice recognition by default, the Github page explains an alternative to go fully local and offline for voice recognition. Being open anyone can connect to new services as these hooks are developed. Would be great if this expanded to work on desktops and speakers.
What's also impressive is the developer is taught himself to use Java to develop this, and he has shared all the code asking others to assist him, or even use it to fork their own creation.