mistergreen, what's the difference between relative spectral sensitivity and photo sensitivity? If they're the same, the trend of the graph looks similar however, the peaks are very far off(1.0 and 0.3). If there is a scaling factor/calibration, it would be worth looking into before spending $17 bucks.
Sorry if my questions/comments sounds dumb, I am no light expert, just want to contribute and point out what I though to be a little bit of inconsistency. Overall, I think you have got brilliant idea rolling!
Edit: I looked at it again and seems like the photo sensitivity/peak of photo sensitivity = relative spectral sensitivity. Is this correct? If it is, it may fit pretty well.