I gotta say it depends on the criteria you were given with the assignment.
A grad school thesis is expected to be a unique work. It can be inspired by other work - such as the work currently noted at kinecthacks.com, but as you say, you'd have to go beyond it a bit and bring your own inspiration to the table. I'd think that your adviser would have some good advice here on getting through the specific expectations of your university.
That said, a grad school thesis isn't the only time that one may be expected to prove that one's work is the first time through a given hypothesis or project. I had to do similarly for an undergraduate project that qualified us for our writing requirement. In that case, it was one of the bigger projects in my time in university and the requirement for uniqueness was certainly above and beyond a typical assignment - my main point is that this expectation can be levied prior to grad school thesis writing. You have to check with your university and any professors advising you to see what the criteria are, specifically. Sometimes the rules get very specific in ways that no one here could easily guess.
All that blathering aside, there's a difference between copying and being inspired by work described on a website. If you read about someone else's work and get an idea to take it one step farther, then you are adding your own insights and direction to it and I would call that "inspiration", not "plagarism".