Would a paper on the integration of multiple technologies make sense?
The general criteria for something being publishable is that it advances human knowledge in some way.  

As you note, it is clear that a scientific publication can be made about the efficacy of your creation at its intended task.  

Whether there is anything else beyond that, however, depends on whether the things that were learned during the development and integration process are interesting and generalizable in some way.  Some possibilities:


Did you have to combine the existing elements in an unusual or unexpected manner?  
Was there a process that you followed that will make it easier to design more things of the same type?
Was this an example of an emerging set of cross-field collaborations that in itself would be interesting to tell other practitioners about? (e.g., is "postural robotics" an area with a lot of potential that other roboticists would like to hear about?)


It might still be, however, that there are no other papers in this particular effort at the moment---and if so, that's OK too.  Don't try to slice the salami any thinner than it should be.