You may want to consider a scientific workflow system. These systems handle both data storage (including meta-data and provenance -- where the data came from), and design and execution of computational experiments. If you are concerned about the complexity of the meta-data (e.g., pH value..) and would like to make sure to be able sort things according to this, you want to give "Wings" a try. You can try out the sandbox to get an idea: http://wind.isi.edu/sandbox.

In the annual RoboCup@home league they have robots following humans all the time and have been for the past few years. It's one of their standard challenges, e.g.: http://www.youtube.com/watch?v=wKfP_Cz9oa0