The picture is blurry and it doesn't enlarge, but I don't think it is hornworm. They usually do not arch like that.
It might be a looper. We call them cabbage loopers or alfalfa loopers, but they feed on many things including tomato plants. They are leaf eaters and don't attack the fruit.
Check for the two pair of "pro-legs" in the middle.
If it is this, it is one of the less destructive pests, will not decimate your plants like hornworms can.
In the long run, what you need is a functioning eco-system in your yard. There are a variety of tiny stingless wasps that parasitize them (as well as hornworms). You can invite these into your yard by growing flowers that have nectar in tiny florets. This includes all the carrot family things (dill, fennel, parsley etc) when allowed to bloom, as well as buckwheat, alyssum, yarrow, marigold, white clover, anise hyssop, and others.
In the short term, if it seems like they are doing serious damage, you can get Bt (bacillus thuringiensis) from a garden store. It is a disease that attacks various caterpillars and nothing else, is relatively harmless in your garden (but note it will infect butterfly caterpillars as well).