Is it worth investing time ? Will i be able to sell the result .
Those are two different questions. To the latter, I'd say: in all likelihood, no. If you're a newbie to Android -and to voice technology-, and working on your own, then it's unlikely that you'll be able to make money worth mentioning with it.
Whether it's worth investing time depends on your personal objectives - you'd certainly learn a lot, but the time spent doing so may or may not be worth it to you.