Using potentially patented tech in a complex hardware/app product

You do not provide a lot of information, so it is somewhat difficult to assess your situation, but if I understand your situation correctly, you have developed a smart home security system which includes what you may suspect is some patented tech. You may be able to obtain a patent for the entire system, however, if you use tech in your system which in fact is patented, you will infringe that patent. TO avoid infringement, you will have to obtain a license to use the tech, and of course pay a fee for the license. Alternatively you can buy the patent outright which covers the tech and then be done with it. Still alternatively, you may cross-license the tech patent holder to the effect that you can use their tech in exchange for them to use your system - cross licenses are often negotiated under such circumstances.