Saw the thread on where to clip your pedometer, on a related topic, I
find you can get fairly decent accuracy with even cheap pedometers if
you calibrate them using a know distance, which can easily be measure
with your car's odometer.  The pedometer has a setting for your stride
length. Put in some figure close to what your stride actually is, then
walk a know distance.  A simple, straight track down a roadside for a
mile is good, again you can easily measure this with your car before
hand.  After walking the know mile, look at what the pedometer indicates
you've walked.  It probably won't be right on the money, but you can
adjust the stride as required to get it pretty close.  Say you put in a
30 inch stride, and after your 1 mile walk, the pedo reads 1.25 miles.
Obviously your stride is too long, so reduce it by the factor of the
error, in this case 1/1.25 = 0.8, so multiply your 30 inch stride by 0.8
& change the stride to 24 inches.  Similarly, if the pedo says .75 miles
after the 1 mile walk, 1/.75 = 1.333, so multiply your 30 inches stride
by 1.333 & change the setting to 40 inches.  In my experience the stride
setting that yields decent accuracy usually isn't that close to your
true average stride.  Also always put the pedo on the same spot on your
 body (I use the spot about in the front of my right leg) and note that
things like an elastic jacket band which may press on the instrument is
likely to affect the reading, generally reducing it.

Dan