Currently contaminants can only be reliably detected with advanced equipment like mass spectrometers that run over a hundred thousand, require clean conditions, trained operators, advanced software, and routine upkeep.
Improvements in these machines would be a huge step in the right direction.
Pretty much the only practical tech right now is a card with a shitload of immuno assays on it, like those pan-drug test strips. There are a pain to validate and expensive/no fun to develop. The business model here would be spending a few million buying antibodies from commercial suppliers, validating tests, and selling cards for <<$1 per test. Test cards would likely be e.g. "artificial hormones", "pesticides I/I/III" etc
Education is also an issue, when the domain of possible contaminants is so large.
The sample prep in this case is still a problem, though. Easy for drinking water, harder when you're trying to take a standard sample of e.g. apple skin
There is a little bit more 'political will' in China because there is greater awareness of food contamination. But the market only supports water conductivity meters and gimmicks like that, unless something's changed in the past year.
The closest thing I think is the "Consumer Physics SCiO," aka the Theranos of chemical characterization. Their device is both too expensive (for a mainstream consumer product) and useless for any real world contaminant test, although it is fine at testing water/sugar/protein content for e.g. bad baby formula
edit: whoops, I missed that by "pick up" you meant "detect", not "munch through"!