Latest guidelines by ESOMAR include specific applications such as mystery shopping, biometric data and in-store tracking.

https://www.esomar.org/uploads/public/knowledge-and-standards/codes-and-guidelines/ESOMAR-GRBN-Guideline-on-Mobile-Research.pdf

Mobile research has been growing steadily in the past 8 years to now account for $1.8 billion global annual turnover. (Source ESOMAR)