Smartwatches and smartphones have their own unique advantages and their combination allows the user to quickly access information. Our proposal, Backhand Display, is a wearable device for the back of the hand. It is a single device that can replace both the smartwatch and the smartphone. Its fundamental performances are evaluated, including text input, vibration notification, and response time between notification and reply. It is confirmed that Backhand Display offers faster text input than the smartwatch, greater notification capability than the smartphone, and quicker response to notifications than either of them. These benefits are supported by the results of a user questionnaire. Though there are several limitations and issues to be resolved, these results show the potential of Backhand Display, a wearable device on the back of the hand.