Omron are about the best of the cheap blood pressure meters, even the automatic machines used in hosptial wards aren't that accurate. I did a lot of research on BP machines and ended up with an Omron myself as they were the best of the cheapies (ie sub 1000 dollars). Needless to say the most accurate BP measurement system is an acoustic transducer with operator but those machines are the size of a small desk! Hg meters are next best and can be sourced quite cheaply along with a stethoscope and with a bit of training a very accurate blood pressure level can be taken. ( I have that too)...
Good luck.