XMEye is a free tool that allows you to connect your Android device to an external recording system. The main requirement is to insert the serial number of each target camera in order to establish a successful connection. All the devices involved in this transfer of data must be located inside the same Wi-Fi network. A big advantage for this application is the support for PTZ control (pan-tilt-zoom), allowing you to remotely control a camera which has this technology incoporated inside its hardware.
After a camera is added, you can see the live preview directly from the friendly user interface. You can even configure XMEye to record video streaming coming from your cameras, and to save this data on your smartphone's storage. This nice software is able to work with serial numbers incoporated inside QR codes each time you plan to add a new camera to your current collection.
Another good feature is the ability to search, in a manual fashion, recording devices located inside your local network.