Soak wooden skewers in cold water for 30 minutes before grilling. Preheat the grill to medium-high heat; grease the grate well. Season the chicken with salt. Cut each slice of bacon into 3 pieces and wrap around each piece of chicken. Alternate threading chicken and apple onto soaked wooden skewers. Whisk the maple syrup with the mustard until smooth.
Place the skewers on the grill and immediately reduce the heat to medium. Cook, basting often with the maple mixture, for 15 minutes or until chicken is cooked through and caramelized.
Use hot mustard in the glaze for sweet and spicy skewers.