Luna Display is a Kickstarter project to develop a dongle for Apple Macs that allows an iPad to be used as a secondary display. The dongle can go in a USB Type-C or DisplayPort output and an app is installed on the iPad. Then the iPad is a second touch screen for an iPad. It can be used as a simple screen extender, or can be used to remotely run apps on a Mac (it can use a pen or external keyboard as well). Latency is claimed to be very low and it uses existing Wi-fi. The project had a target of $30,000 but had nearly $600,000 of support when we checked. An adaptor costs $65 (19% below eventual list) if you are quick!
Delivery is forecast for May 2018.