Good Question Gabmon. You asked about quick protection for your app prior to release.
My answer here focuses on legal questions. Successful protection of software often relies on both legal rights and practical steps. I lock the door of my house even though the law says I don't need to and someone trespassing could be jailed. In the same way, you may be able to use some sort of DRM / Compiling / Etc. to block folks from cloning your system. Of course, that approach only goes so far and will not deter motivated parties.
Copyright: This forum is focused on patent law, but you should be aware that software code is also protected by copyright. Copyright protection is simple because it is created as soon as you save the file on your hard drive. You may want to include a copyright notice, such as "Copyright Gabmon 2013." The notice is not actually required but will remind some folks not to copy. If your code is valuable, then you'll probably want to register your copyright with the US Copyright Office. A good source of knowledge on registering a copyright for software is available here. http://www.copyright.gov/circs/circ61.pdf.
Copyright is somewhat narrower than patent law because it does not protect your functional idea but rather only the written expression of the software code. However, this seems to addresses the concerns that you have of someone who may "clone my app." Copyright would not protect you against someone who figures out how your app works and then completely rewrites the code without copying any of the code. (Note - there are some caveats here, but this is roughly the law).
Despite the prevalence of creative-commons licenses, the default rule for copyrighted works continues to be that the rights-holder does not want his work copied.
Patent: On the patent side, you only have protection once you have filed a patent application and that application has been examined and issued as a patent. You may have a non-obvious idea that is patentable and current best practices in the industry are to file for patent protection prior to any public release. It is possible for you to file your patent application within one year of the public release. However that approach lends itself to a variety of problems, including evidentiary (he-said she-said) problems. If you wait more than one-year then you entirely lose the ability to obtain patent protection.
Contract: If you are doing a release to only a small group of individuals, it would be possible to get them to sign (click-through) a contract where they promise not to clone your work or to share it with anyone else.
Temporary Protection: (1) You have copyright protection in the software, and you might want to go ahead and register that copyright; (2) If you think you can get a patent, you may want to file prior to public release.