What about 3rd party keyboards like those that have recently made their way to iPhones and have been on Android for a while? All of them (even Samsung's swype

What about 3rd party keyboards like those that have recently made their way to iPhones and have been on Android for a while? All of them (even Samsung's swype style keyboard) seem to have some sort of cloud-based storage for your data so it can remain equally predictive across your devices. Is there any good security research out there on how safe these keyboards are and which ones are the worst offenders? Seems like it is essentially a user-installed cloud-based keystroke logger ripe for abuse. I love the functionality of some of them, but man do they terrify me.