Endurance Training Week 2

Yesterday we did a shorter, faster workout about 3 miles of alternating trot and canter.  Khari was a little warm and breathing fairly hard but she recovered pretty quickly. Within about a quarter mile of walking her breathing and heart rate had visibly come back down.  I am trying to find a heart rate monitor and GPS specifically designed for endurance riding.Today we rode for 2 and half hours.  Started off at a walk.  Trying to get her to extend her walk.  Some luck today.  Khari was a little full of herself because she had been in her stall due to heavy rain, but calmed down into a fast trot after about 15 minutes.  Very little cantering today.  Maybe half a mile at most.  It is hard for me to keep track of the distance.  I think I really need the gps system that will keep track of my mileage, mph, and our heart rates.Khari seems to be handling the work load pretty well.  I switched to the western saddle the last two days to help her get used to the heavier weight.  I am going to have to pack weight though because I am below the feather weight division.  The western saddle caused a little soreness and I am going to go back to the english saddle for the extended corral training.  I just haven't made a decision on a good endurance saddle yet.  My husband is convinced that we need to build one because he is not happy with the weight distribution and the potential for sore spots on a 100 mile ride.  Technology has come a long way and he is surprised that there are not more exotic materials used in endurance saddles.  He has a couple of engineering buddies that might work on the problem. 
I have been washing her off when the weather permits and it is not to chilly and rubbing her down with Sore NoMore or some kind of linement.