If you need to test each device and combinations, you would need to test all $2^3$ combinations. To test this for each person would take 80 trials, not thirty. (The test plan you have would only show interactions and not the main effects for your devices).
The fewest trials could be run with a $2^{3-1}$ fractional factorial design. Each of the devices would have two levels (worn or not) and each device would count as a factor. With this test, and four runs per person, you would be able to, in 40 tests, have every person test every combination of wearing the devices, including the main effects of only wearing a single device. this fractional factorial design dos have a resolution of III, and generally should be avoided, if possible.
If you can afford it, conducting a full factorial design ($2^3$) for the three factors would yield the most information about main effects, interactions (AB, AC, BC, and ABC).
You may also want to look into the "Taguchi" or "Robust" designs of L4($2^3$) or L8($2^3$), which result in the same number of runs per individual but yield different analysis tools and results. Another option to consider with the Taguchi designs is drastically reducing your test runs by having the individuals in an outer array as a noise factor, and not required to perform every test. As I recall, this could easily cut your trials from 40 to 20, or even 10, if the loss in data resolution is worth the savings in running experiments.
The NIST website has a decent tutorial on choosing and implementing designed experiments: http://www.itl.nist.gov/div898/handbook/pri/section3/pri3.htm and http://www.itl.nist.gov/div898/handbook/pri/section5/pri56.htm
