Personal assistants are hot these days. Open source personal assistant is a dream for many developers. Recently released Jasper makes it really easy to install personal assistant on Raspberry Pi and use it for custom voice commands, information retrieval and so on. Jasper is written in Python and can be extended through the API. More importantly, Jasper uses CMUSphinx for offline speech recognition, so much waited capability for assistant developers.
Try Jasper, download it's source code from Github, modify it according to your needs and contribute new features.
We wish all the best to Jasper project and hope it will become popular.