Uh, uh, not very well defined? A good project is very subjective term. Something good to you isn't neccesary good to your mentor. Something stunnignly good to me might not impress somebody else at all...

As for unique part, it is heavily dependant on your local situation. I might mean either: my mentor is not aware of it, not done as degree paper before on my university or never done at all in the whole history of mankind.

You are certainly aware (thus far in your education) that in picking your project you are limited only by your own imagination (the beauty of embedded), right? And that you can desing anything ranging from brain teasers, small house utensils, over vehicle add-on to UAV brain, rocket on-board system, telecommunication equipment to mobile robot platforms...

So my advice is: Think hard what you would like to work after you get your degree. Picture where you would like to work for example. Than pick something related (not neccessary uniquie, sometimes a small improvement or even conceptual awareness means a lot) and do it as your project. So you'll have good reference when applying for your dream job.

Best luck,
CN