There are some healthy, low-calorie protein snacks at your local supermarket or convenience store. Look for any of those healthy, convenient products. Many of them are obviously low in calories, but sometimes you might need to be watchful with portion control. For example, a protein bar that says it has 80 grams of protein may really only have 60 grams if you have a big meal to fill.
Some healthy alternatives to beef jerky include: soy cheese, veggie sausages, popcorn, chicken nuggets, soy bean dip, and tuna salad. To satisfy beef jerky cravings, try making your own beef jerky at home. If you're not too good at this, try buying a pre-packaged beef jerky from your supermarket; you can usually pick these up for only a few dollars. If you are feeling adventurous, try making your own marinara sauce, hot peppers (sometimes this works as a great snack food too), or even ground beef. All of these dishes can be prepared easily in a blender.
If you want more energy, there are other types of protein snacks that will help satisfy that cravings for energy. High fiber snacks, such as granola bars and trail mix, contain high fiber grains that give you energy without packing on the pounds. Other energy snacks that are also high in fiber and low in fat are applesauce and pretzels (these are examples of good food choices with a low glycemic index). There are many other types of nut bars and crackers that are better than any protein snack bar you can buy. A lot of health books and online nutrition information will give you examples of healthy snacks that satisfy hunger and help you stick to your diet!