Synchronize data between 2 instances of SQL Server Express?

I am building an application with a SQL Server 2005 Express backend. I
would like to create a secondary instance the database on another
server that will serve as a fail-over in case the primary server goes
down (there is only the Express version of SQL Server in this picture).

I see that replication in SQL Server Express only works as a
subscriber and not a publisher. Can anyone suggest a method that I can
ensure that both instances of the database propagate data between them
when they are both available? The app is written in VB.Net.

Thx,
Marcus