The Bootstrap I purchased did not sync between the sensor & smartphone. After much elimination your support team decided to mail me a replacement sensor after I returned the defective sensor. However after nearly three weeks the replacement sensor was never received, even after returning the original defective sensor in your prepaid shipping label. I returned the balance of the Biostrap items, straps, charger & cable for a full credit. The whole process took one month from my original order to never getting back to a device that worked. Support by Biotstrap is not great, can only contact them by email. There is no telephone number for a real customer support system Am not sure when and how much I will receive back on the returned device, despite paying in full for a supposedly working device. Overall a little disappointing to say the least. Richard Paris