Heat olive oil in a large skillet over medium-high heat. Add onion and saute 3 minutes then push far to the side.
Add chicken, season with salt and pepper and cook until golden, about 2 1/2 minutes per side.
Remove chicken from skillet and transfer to a plate, while leaving oil and onions in skillet (if you don't have much oil left you can add another 1/2 Tbsp). Add garlic to skillet and saute 20 seconds.
Add balsamic vinegar and cook and stir until reduced by half, about 1 minute. Stir in honey then add in peaches and tomatoes and toss, season lightly with salt and pepper.
Return chicken to skillet, nestling between peaches and tomatoes, cover skillet with lid, reduce heat to medium-low and allow to simmer until chicken has cooked through (it should register 165 degrees on an instant read thermometer), about 6 - 9 minutes.