A while back i got a Yubikey Neo and a Neo-n they are cool little devices that can work as the second part of a 2 factor authentication. The Neo apart from usb also supports Nfc so it can be used with most modern Android phones. So here’s a short summary of how to get it all working. To get everything to work you need to install the KeeChallenge plugin in KeePass, I used the latest version (2.29) when setting everything up. The trick is to put the password file on something shared that everything can read usb stick, Dropbox or similar.
KeePass on windows
For windows follow this guide. Don’t forget to copy the files from the YubiKey-Personalization release.
KeePass on OSX
On OSX the use following guide. A bit more hands on work but just follow the steps. Currently it seems like mono 4.0.2 doesn’t work so go with 4.0.1.
KeePass on Android
On android you need the Keepass2Android Password Safe and YubiChallenge and a phone that supports Nfc, most modern Android phones do.
iOS
Nope, return in a couple of years when iOS has working nfc support