Is there a good (free) web app to track blood pressure?

My doctor has requested that I take my BP on a twice-daily basis, and bring the printed results to her during every office visit.

At first I was just using a spreadsheet to do this, but then I tried to get creative with it by adding an entry form and graphs. I realized at this point that I was probably reinventing the wheel because there are web apps for everything these days.

A quick Google search didn’t turn up anything promising, and the health websites I use regularly (traineo.com, mapmyrun.com) don’t seem to support these features as of yet.

Thank you in advance for your suggestions.