In regards to everyone claiming calibration as an issue for court - they're absolutely right.
For instance - if you're stopped for speeding, if the device wasn't calibrated right before use, then the citation can be dismissed on grounds the device wasn't properly calibrated - this will work for most cases as most speed detection units manuals state they need to be calibrated before each use... On a side note - the posted speed limit isn't the legal speed limit - you can ask for a traffic survey to be done which will tell you the legal speed limit ( which is the average speed of the whole for the area during the same weather / light conditions - obviously people will be going above the limit, and below - but the average is the legal speed limit and there is a legal precedent for this )
Now - you could build your own unit to get a general idea, and you can log that data... However, if you want that unit to contain any weight in court you'll need to hire an expert witness to corroborate your findings and someone to verify that your sensor is within spec.. Otherwise the defense will have the case dismissed because 'homemade' electronics aren't 'scientific' enough to prove any wrongdoing... If you're unlucky the case will be dismissed with prejudice meaning it can never be tried again... They will ask for that if the opening is weak or the evidence is that poor - although a judge will likely NOT do that especially if you argue people are getting sick - and you can then ask for a continuation in order to hire an expert witness, and to have additional testing done...
However, it's best to have all ducks in a row before you take it to trial, otherwise you'll end up making the judge feel like their time is being wasted.
Now, depending how large whoever it is you're going up against - for every expert witness you hire, they'll likely have 1 to 10 saying otherwise... So make sure whoever you hire as an expert witness, calibrator, or company to perform the scans are legitimate, top of their field, honest with integrity so they can't be dismissed on the stand... So it can't be anyone that's worked for the company as your primary - they can be a witness but they can't be THE witness because if they were fired, or whatever.. the defense will argue motive to falsify testimony and it'll make it look like the person isn't credible at all....
Be meticulous about gathering information - make sure any witness / expert witness who speaks, is subpoenaed, or is hired doesn't have anything which can kill their credibility otherwise you're done...