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Do you guys know where I can get the resources to build my own digital assistant?
Form a software startup. Find some investment capitalists who are willing to fund it. Then hire a bunch of really smart computer engineers who have spent years studying software, hardware, speech recognition, and AI. Also get some managers to motivate them, and some HR people to keep everyone in line. After a while, add a marketing team to push your brand and a sales team to sell the product they have created.
On a more serious note, your question is very broad. What exactly do you imagine such an assistant would do? Would it run on your computer, or some external hardware? Will it listen for your voice and accept voice commands? Or will you just type commands at it? Do you want it to look things up for you? Have access to edit your computers' files? Will it be integrated with your OS or not? Are you planning to write it in Processing?
If you are doing an art project or a demo then there might be ways to lightly interface with an existing speech-to-text engine -- like a Google or Mac cloud API or OS built-in.
However, given that your previous question was about AdMob, I'm guessing that you want to interface a mobile Processing app with speech recognition for the purposes of a commercial application? Perhaps on Android using the Android Speech API...? We really need a lot more detail to understand your question.