I appear to have done something wrong here, so let me try to rephrase this more simply so I stop giving the wrong impression.
I'm in the planning stages of a project right now, on my own time; I'm currently defining the scope of the project. I can see this application also releasing an Android app; furthermore, I've long wanted to get into Android development, and being able to list an actual project on my resume seems likely to be beneficial. However, the application itself is far more useful on a PC than a tablet and almost useless on a smartphone; odds are, very few (if any) people would want to use this on Android.
I want to develop it, but I anticipate almost no demand. Should I do so under the idea that the experience is useful, or should I either keep it private or not do it under the idea that an app nobody uses looks bad to future employers?
I'm planning out an open-source project, mostly to beef up my resume (ETA: Okay, I'm doin it mostly because I want to do it, but I'm releasing it as open-source rather than keeping it to myself so I can list it on my resume easier). I'm considering doing an Android version, intended to run on tablets. But it's not the most useful thing to have on a tablet; neither I nor my partner can really conceive of anyone wanting the product. However, adding "developed for Android" to my resume seems to be a good selling point, and I'd like to get into mobile development. Should I make an app nobody wants so I can say I made an app? Or should I hold off until I have a better idea?
Edit: I must have phrased things badly, some of the answers seem to have the wrong idea. I'm doing the entire project for the hell of it; if I don't do an Android version of this particular project, I'll complete it sooner and plan something else and do that. It's a given that I'm always going to be doing a project and that I want to do this project. The question is, should I instead do something more useful as a "let's play with Android" project? Will making something nobody wants hurt me in the long run?