Mix tomatoes, bell pepper, cucumber, celery, onion, chives, vinegar, lemon juice, Worcestershire sauce, pepper, salt and hot sauce in a large bowl. Cover and chill for at least 20 minutes or up to 1 day.
Mix shrimp, garlic and thyme in a medium bowl; cover and refrigerate for 20 minutes.
Coat a grill pan with cooking spray and heat over medium-high heat or preheat the grill to medium-high and oil the grill rack (see Tip). Cook the shrimp until pink and firm, about 2 minutes per side. Serve the shrimp with the salsa in martini glasses or bowls.