Generally speaking, there is no such thing as a "patent on a product" (with the exception of design patents and the like). Rather, individual aspects of technology can be patented. Such a patentable aspect has to solve a technical problem using a technical solution to cause a technical effect. Generally, one cannot obtain a patent for instance on the overall appearance or a generic formulation of the "purpose" of a device. The first question would be, do you have a good idea of what such a technical aspect would be? And if yes, is it actually necessary to reveal your technical solution in order to market your project? Generally, you should be able to make the public claim that your product does xyz and/or does it in a better way, if you do not reveal HOW it does that.
Obviously, this is a tricky issue, and filing a patent application (then with an as-detailed-as-possible description of all potentially patentable aspects) is the only sure way to secure a priority date.
Also, you have to decide what your main objective is: Do you want to prevent other people from copying your idea, do you want to prevent them from getting a patent on the same idea first, or do you want to make sure that you will be able to obtain a patent at a later date yourself? These are slightly different issues and may require different strategies. A defensive publication, for instance, precludes competitors from obtaining a patent on the same idea, but also yourself. And since your idea has been published, you can be sure it will be copied if it is relevant.