meteohub.de

Does anyone know of a compatible instrument for meteohub just for temperature measurement?

one of these USB Thermometers that have recently been added to the supported devices list.
a 5m USB cable and you´re outdoor. with an USB Extender using Cat5 cable even longer distances shouldn´t be a problem.

Otherwise RFXCOM working with nearly all the Oregon Scientific sensors is quite a simple solution.

A 1-wire probe is appropriate and quite cheap (30 euros). But it's only supported via plugins and you hav to know how to handle the linux meteohub is based on.

A wireless with a receiver with usb connectioen would be good. Then I can place that a more strategic place than my main weather-station with wind and rain sensor.