You might want to see my Bilko Index calculator, which is very much in beta form:
This link takes you straight to the Bilko Index survey, which asks consumers how much of brand name pesticides they use and then calculates an index value that is intended to be representative of the toxicity due to their use of that product. Something like this would be a tool to inform a household EMS, not the EMS itself. The formulas are simplistic but they do get the consumer to reflect on the aspects of use that mostly determine the extent of toxicity (what product, how much is used, how is it used). The site has information about how the index is calculated and what data are used if you're interested.
I'd like to see it expanded to include not just household impacts but local impacts and global impacts due to consumer choices.