hi, if you are in the UK the ones lloyds pharmacy sell for £9.99 are very good. You would be better getting a proper one with arm cuff rather than the wrist ones, I have found these inaccurate. If you have problems with your bllod pressure it may be worth getting one, but only if you know what you are doing, what the reading actually means and what is abnormal in you.
A lot of people buy these machines and do not know what the results mean and this can lead to stress
and .. high blood pressure