In general: Since every octave means a doubling in pitch a purely linear behaviour is not very practical. If the sensor itself acts linear, and it normally will because a doubling of the length will lead to a doubling of the registered resistance, one wil have to convert the signal soemwhere else along the way to solve the pitch issue.
I use a Doepfer R2M ribbon controller. It also offfers pressure sensitivity which adds another layer of expression, the most obvious choice being to attach the filter frequency to pressure. Furthermore it has a complete MIDI and CV interface on board and a lot of extra features like an arpeggiator.
It is however a bit underdeveloped as a Trautonium / Ondes Martenot type controller. You can for instance not set the velocity of the MIDI notes. Mine has been modified but as standard it always sends MIDI velocity value 127 with each note! It's a like Doepfer lost their way a bit after the solid state Trautonium project.
I actually designed a visual scale to help with playing melodies on ribbon contollers and also wrote an article about my experiences. You can find it here:
Building a ribbon controller yourself is of course way cooler but the basic requirements and practical considerations are the same so this might still be off interest to some of you.