In fact, there's a whole Wikipedia page dedicate to Malaria testing:

http://en.wikipedia.org/wiki/Malaria_antigen_detection_tests

And they note more than 20 commercial products for sale that test for Malaria.

Here's a paper from the NIH on the importance and state of rapid Malaria diagnosis:

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2223842/

Here's another NIH paper talking about an Malaria eradication, and a big part of their plan is diagnosis:

http://www.ncbi.nlm.nih.gov/pubmed/21311583

Again, I'm not expert (or even novice), but looking at the literature and what people in the field are working on -- it looks like they make use of diagnostic tools for Malaria. I've certainly seen no papers saying that diagnostics isn't useful in 99.99% of all cases, just pop a pill. Not saying that that's not what should be done, but I find the evidence thus far lacking.

"Clinical diagnosis, the most widely used approach, is unreliable because the symptoms of malaria are very non-specific."

From the last NIH paper I referenced, "Many of malaria's signs and symptoms are indistinguishable from those of other febrile diseases."

Here's a paper from the Lancet about Malaria misdiagnosis:

http://www.ncbi.nlm.nih.gov/pubmed/15555670

From the above: "Effective and affordable treatment is recommended for all cases of malaria within 24 h of the onset of illness. Most cases of "malaria" (ie, fever) are self-diagnosed and most treatments, and deaths, occur at home. The most ethical and cost-effective policy is to ensure that newer drug combinations are only used for true cases of malaria. Although it is cost effective to improve the accuracy of malaria diagnosis, simple, accurate, and inexpensive methods are not widely available, particularly in poor communities where they are most needed."

Additionally people apparently can build up a resistance to the Malaria treatment. See:

http://www.irinnews.org/Report.aspx?ReportId=78014

“When people are sick in Mali, the doctor will usually tell them they have malaria whether or not they test for it,” said Fatou Faye, an infectious diseases researcher and trainer at a privately funded medical laboratory, the Charles Merieux Centre in Bamako.

“The patients then buy anti-malarial drugs in the street and build up a resistance to treatment.”

As a result, according to research by Dr. Imelda Bates at the Malaria Knowledge Project (MKP), part of the Liverpool University School of Tropical Medicine, this means people miss other causes of feverish illness such as pneumonia and meningitis, which can cause further illness and even death.

Again, I'm not saying your wrong necessarily, but everything I read seems to point to the fact that low-cost accurate Malaria diagnosis would be useful.

Actually you're telling him that he's acting exactly like people commonly do in malarial areas, and are informing him that simply taking that course of action breeds worse varieties of malaria, and causes people to die of unrelated diseases that could have been treated.

This strongly suggests that he has practical experience with malaria. And is useful information for him about how the advice he has based on experience is suboptimal.

When it comes to peoples lives, people very quickly reach the optimal solution. It's what humans do best. This android solution is a theoretical solution from people who have never experienced malaria and don't even live in an area where malaria exists.

Yes, I have practical experience with malaria. I also have practical experience with android phones. I am actually qualified to make experience-based judgments on the feasibility of that tool, and quoting theoretical papers may win you arguments on the internet, but it will have little practical usage.

When there is a disease in an area that has existed for so long that people have built genetic resistance to it, at the cost of having occasionally sickly children, then trust me, modern methods that work will quickly be selected.

Modern methods that don't work (bed mosquito nets), will be selected away.

Armchair solutions for problems you only partially understand are pointless.

From WHO/USAID report on Malaria detection (executive summary):

"In malaria patients, a prompt and accurate diagnosis is the key to effective disease management. The two diagnostic approaches currently used most often, however, do not allow a satisfactory diagnosis of malaria. Clinical diagnosis, the most widely used approach, is unreliable because the symptoms of malaria are very non-specific. Microscopic diagnosis, the established method for laboratory confirmation of malaria, presents technical and personnel requirements that often cannot be met, particularly in facilities at the periphery of the health care system. In addition, delays in the provision of the microscopy results to the clinician mean that decisions on treatment may be taken without the benefit of the results. Thus, the recent introduction of rapid diagnostic tests (RDTs) for malaria is of considerable interest."

This android device is solving a solved problem.