If your product is not one that can be patented, you still have several options in the form of trademarks to help protect your investment.
Trademark the name of your product. You will be putting a lot of time and money into the marketing your product, and, should one of your competitors copy it, you don’t want them to be able to use your name. This is true especially if you’re the first one to market and you’ve established your product as the dominant one. Apple is going to court now with a Chinese firm over the use of the word “Ipad,” which shows how important branding is.
You can also trademark the shape of your product. If there are distinguishing features of your product that are proprietary to you, you can trademark them. For example, I believe that Coke has trademarked the shape of the Coca Cola bottle. I’ve also heard that it may be possible to trademark a sound, as Harley Davidson is said to have attempted to trademark the sound of their motorcycles.
Once you’ve decided on a name for your product, the first step in getting a trademark is to have a trademark attorney do a search for names registered for similar products. This is the safest way to proceed. Once you’re in the clear, it’s easy to file a trademark application with the US patent office. I’ve done it myself in the past.