Service dogs work hard, including Alert dogs. For this reason, they require a way to unwind from their work day that doesn't add to the stress they could already, potentially be feeling. A great way for them to unwind is with a chew toy. It helps prevent burn out, and it is a low-impact way to just relax for a while. Remember there are many different types: raw bones, rubber toys, classic Nylabones, to name a few. Do your research and get something you're comfortable with.
Alert dogs already know how to sense things and call for help. They make great service dogs for diabetics, but more than that, great companionship. If you're looking for a way to add to your dog's skill set, go for hand signals. It helps the dog understand you even when you can't speak, for whatever reason, and can result in some pretty amazing rescue missions if anything were to happen.