Smart and wearable devices are trendy electronic objects that have become increasingly popular in recent years. Those devices are, by definition, tightly connected with the user's personal activities. Authentication is therefore a critical feature for both identifying users and personalizing the services on the device. In particular, the emergence of smartglasses changed the way we thought a wearable could assist users in their daily activities. As designed by commercial providers, smartglasses are sold with a very specific set of interactions capabilities. These capabilities have a strong impact on how comfortably or safely users may authenticate to their smartglasses. For this reason, we investigate in this paper the different authentication methods available for smartphones and we comparatively position the smartglasses in the design space of authentication methods. We propose a new approach based on touch input on an arbitrary surface using thermal camera input. This approach aims to circumvent the lack of touch surface provided by smartglasses, while maintaining an acceptable level of security.