Ereader

TLDR: Im looking for an ereader that will sync my progress with an app on iphone so I can continue reading if I dont have my ereader.

I currently have my books stored in a calibre library, most in epub format, on my computer and manually load them onto my nook or phone. My ereader is on its way out though and I was wondering if theres a better solution.

From what I've read, most ereader/app pairs only sync if you buy them from the respective store.

Thanks in advance