In the German QRPForum someone mentioned a group of QPR enthusiasts QRPGuys. They have some neat QRP kits - transceivers as well as antenna-tuners.
I gave these kits a try: QRPGuys Portable Tri-Band Vertical Antenna and the QRPGuys 40m-10m UnUnTenna Plus 
This post deals with the second one - the QRPGuys 40m-10m UnUnTenna Plus.
This antenna tuner consists of an adsorption brigde to check tuning and the tuning circuit itself:
First I've build the antenna as described in the user guide using a 29' (8,84m) radiator and a 35' (10,67m) counterpoise.
The antenna has her first mission behind. I've used her on the summit "Kaltes Feld" and she worked very well.