Basically, both of your nodes are identifying transactions that belong to particular public keys that are contained within their respective wallet files. So, it would appear that you either have the same "wallet.dat" on each node... or the wallet files on each node contain the same public (or private) keys.
The way you have setup your network really makes no difference, neither does the "addnode" commandline args etc... The only way for this to happen, is that both nodes have the same keys.
Edit: just noticed they both have the same balance and same transaction history.
This pretty much confirms it.
Edit2: Made payment on one node, and a minute or so later, the other node also gave a transaction sent notification, but not recieved twice in mobile wallet.
It isn't making a second transaction... it is just "seeing" the original transaction.
Think of it like looking at your internet banking on your desktop computer (node 1)... and sending money to a friend.... then you look at the internet banking on your mobile device (node 2)... it'll show the same transaction, but doesn't mean that you have sent the money to your friend twice!
![Tongue](https://bitcointalk.org/Smileys/default/tongue.gif)