Is there an app?

Yes: the Carnoat app for iPhone and Android is coming soon. It opens your archive as on carnoat.com, with what a phone does better: scanning an invoice or work order with the camera (the pages become one PDF), sharing an invoice from your mail or a photo from your camera roll into Carnoat, notifications when a document has been read, and Face ID or your fingerprint to open it. Without a signal, an upload waits on your phone and goes as soon as you are back online. The same rules apply as on the website: the same redaction, the same checks, the same credits. Until then, carnoat.com works in your phone's browser, camera included.