Only standby Server in Cloud(Amazon), not the primary

In PostgreSQL 9.x, using Streaming replication (hot standby with PITR), is it possible to have just the standby server in Cloud(Amazon) and the primary database local ?

What I am trying to achieve is get the backups guaranteed in cloud, if I just have my standby server there ?

Is it technically possible ? What are the risks and performance issues ?

Thanks,

-Bala