How does a software application idea become a research project?
Your software idea may be able to become a piece of research if you can come up with a few things:


Research question. Ask a question relating to your software idea - for example, "How can we do X?" "What is a better design for X?" etc. Check the literature to see what has been said about this question (and related questions) by others.
Research result. What is the actual, novel contribution of your work? Is it a new technique that hasn't been done before? A rule of thumb for designing certain kinds of applications? A much better way to do a certain kind of task (for some reasonable definition of "better")?
Validation of research results. What kind of convincing evidence do you have that your result is sound? Depending on the type of result you claim, your evidence may be in the form of performance benchmarks of your technique relative to state of the art, user studies from users of your application, or something else entirely.


The best way to get a better understanding of what constitutes a research question, research result, or evidence, is to read a lot of papers in your field of interest.