The KardiaMobile requires a one-time purchase of $99, while the KardiaMobile 6L is a one-time purchase of $149.99 (currently available for pre-order). If you’d like to add on the optional Premium Protection Plan (which includes Device Replacement, Cloud Storage and Security, Personalized Heart Health Report and Medication Tracking), that costs $9.99/month or $99/year. If you get the KardiaBand (compatible with the Apple Watch), that requires the purchase of the Premium Membership, but Premium is optional for the KardiaMobile and the KardiaMobile 6L.