As the landscape of wearable devices continues to expand, power remains a major issue for adoption, usability, and miniaturization. Users are faced with an increasing number of personal devices to manage, charge, and care for. In this work, we argue that power constraints limit the design space of wearable devices. We present AlterWear: an architecture for new wearable devices that implement a batteryless design using electromagnetic induction via NFC and bistable e-ink displays. Although these displays are active only when in proximity to an NFC-enabled device, this unique combination of hardware enables both quick, dynamic and long-term interactions with persistent visual displays. We demonstrate new wearables enabled through AlterWear with dynamic, fashion-forward, and expressive displays across several form factors, and evaluate them in a user study. By forgoing the need for onboard power, AlterWear expands the ecosystem of functional and fashionable wearable technologies.