I have a Kardia Mobile but I believe I get a lot of false readings. I use a Oxymeter on left hand and blood pressure kit on right. The heart rates usually match. Then I use Kardia Mobile and it says I’m in Tachycardia. I believe if you have arrhythmia, you can’t get a true reading. My EP told me to put it up and only use it if I have other symptoms like chest pain, dizzy, passing out.