You're going to need a trained human in the loop just to handle the blood and apparatus in a sanitary way.
Humans are inherently better than any app at the image task, so why not just let the human do it?
This looks like a non-solution to me.
Moreover, as the software is improved, updating the software -- and raising the baseline of quality -- is a unique advantage over the "just use humans" solution.
The scenario is "person trained to work with blood samples without spreading/contracting HIV deployed into field packing a small digital microscope and support software built on WP7." This person is likely already doing a variety of other community medicine and is the closest thing to a medical doctor many of their patients will ever see.
There's no argument against giving the practicioner a helpful tool, only that it may be automating an insignificant part of the overall problem (looking at the image).
So...it's a microscope lens for a smartphone? Isn't that something already developed? What about this app "detects malaria"?