Keep in mind that alot of cuff readers are inaccurate for anyone that trains hard.
If you walk into a Fred Meyer or Wallmart and read the notice next to a blood pressure cuff they typically say that readings are inaccurate with arms over 14".
I agree with all above... The store ones don't fit me, unless I really jam my arm in; totally straight. The home upper-arm ones are probably the best, since some can be had with large size cuffs . I have a Panasonic, which is the best overall I've tried. The wrist ones are a total joke; at least for me. I've tried several, all of which read WAY WAY high.
The other thing for accuracy, is to test about 5 times over the course of at least 15 minutes. Then average it. Measuring once, is totally useless and false. Your numbers can go up or down 20 or 30 points in a minute or two, so an average is the only good calculation.