it is free of charge, from the maid's poin tof view
but actually employer pay already which is part of the OWWA (something like this, maid's union)
back to the point about the machine,
it is not worth to buy because the maid has only one occasion of high BP
you can counter-suggest the doctor to recheck your maid's BP, say 15 - 30 minutes later (honestly, this is the usual practice)
which doctor, unethical !
BTW, ask your maid to record the BP readings on a little book & show to the doctor in next consultation
why did the maid go to see doctor for checking the BP