I think I know this, but I am reluctant to solve it too quickly. If I am right Daniel has hit the family and it is one of the most requested plants in the Sourcing forum.
Yes, it's the fruit of Murraya koenigii, or if you prefer, Bergera koenigii, the curry-leaf plant. It's fruiting right now in my suburban backyard, which is something of a heat trap. Around here is probably getting close to its climatic limit, especially for fruit set. The fruits have all turned glossy black this week. Separating Bergera from Murraya appears to be justified scientifically. Judging from one published study based on chromosomal evidence, they should even be placed in different tribes of subfamily Aurantioideae.
Daniel helped :) That was fun because it is a plant asked about on the forums, but many growers of the plant (around here at least) might not ever see the fruit on their indoor plants!