There're no cartridges needed; the custom paper has the ink already embedded. No need for WiFi, or even Bluetooth pairing either, since Prynt runs on its own battery.
Perhaps most impressive is the range of devices for which Prynt is outfitted. It'll work on iPhone models 5 through 6, as well as a number of Android options. And if you upgrade, you won't need to replace your whole case—Prynt is modular, so you can simply switch out the dock component that affixes to your smartphone. The magic can all be yours by pledging $99 on their already-fully-funded Kickstarter.
And yes, of course you can add a filter.