Siri competitors for Android are a dime a dozen, but the latest alternative Evi may have the winning combination of a voice recognition engine that actually understands what you say and what (we hope) appears to be a natural language processor that can figure out what you want.
Unlike a standard search engine which performs keyword searches, Evi aims to answer your query with a specific response. So, for example, if want to know what the capital of France is, you would ask Evi "what is the capital of France?" and Evi would respond "Paris". Evi is also good with contextual questions, so if your next question is "is it dark there now?", Evi would understand that you want to know whether it is past sunset in Paris.