Preheat the grill to a medium heat. (When ready to cook, spray the rack--off the grill--with nonstick cooking spray. In a large pot of boiling water, cook the potatoes for 10 minutes to blanch. Drain.
In a small bowl, combine the honey, mustard, lemon juice, thyme, and pepper. Add the chicken and mushrooms, tossing to coat well.
Alternately thread the chicken, mushrooms, tomatoes, and potatoes onto 8 skewers. Grill the kabobs, covered, turning occasionally, for 8 minutes or until the chicken is cooked through. Divide the skewers among 4 plates and serve.