I use a Cateye Strada double wireless computer on my bike which shows cadence. I find it very useful when I am riding with my bike hooked up to the trainer. I find that by simply switching through my gears and keeping my cadence at around 95, which in turn raises or lowers my speed for a given time, also resistance, I can get a pretty decent workout in. If I want to go all out for 30 seconds, switch to the big gear and get my cadence up to 110 or so, hold it for a given time (usually 30 seconds) then back off and downshift for an much easier spin for about a minute or two. I do this about 15-25 times and it feels like a good workout. If I didn't have the cadence sensor and only had the fork sensor, I would not be able to measure anything, so in that sense its important to me.