I had a thought recently.... follow me.
It's been established that smell is the sense most closely related to memory. Many of us have experienced this (I do constantly): walking through a mall or a park or a place with smells... and something or someone suddenly comes to mind, seemingly out of the blue. A split second later, I realize it was cued by whatever smell I just encountered. Memories flood back very clearly.
So I got to thinking.... one of the necessities of effective language learning is a good memory; the increased retention of information obviously provides a greater return on your investment of time you devote to studying.
I did a cursory google search to see if anyone else had considered this, and there was only a small glimmer of hope. More on that later. I give you: the limbic system.
Wikipedia tells us that "the limbic system (or Paleomammalian brain) is a set of brain structures including the hippocampus, amygdala, anterior thalamic nuclei, and limbic cortex, which support a variety of functions including emotion, behavior, long term memory, and olfaction."
In as little detail as possible, the other little tidbits of information that seemed relevant were the dentate gyrus, which "is thought to contribute to new memories" and "is notable as being one of a select few brain structures currently known to have high rates of neurogenesis in adult humans." The entorhinal cortex (EC) is an important memory center in the brain. [It] forms the main input to the hippocampus and is responsible for the pre-processing (familiarity) of the input signals." The hippocampus is also a big important chunk of the brain dealing with long term memory. All that is to say that it makes sense that the olfactory system (and it's relation to memory and emotion) easily prompts us to recall very clearly things that may not have crossed our minds in ages.
The wrench in the gears is finding/creating a synesthetic-enough correlation between emotional memories and cold hard linguistic knowledge, which usually doesn't carry any emotional weight. However, if there WERE any relation, think of the impact of having the near-total recall with language as we do when we (arguably involuntarily) recall a long-unthought thought.
But again, in a practical sense, how does one combine the general experience of those two senses in a linguistically relevant way? It didn't seem to make any sense until I found an article written by a doctor working in the field of deaf-blindness who is currently working to use the sense of smell to improve (what I suppose you would call) comprehension of objects and their surroundings.
Unrelated application? Yeah.
Possibly very strong means of communication with someone who has no other means of speaking (as are, to a certain degree, students of a new language)? Yes.