He went online and told meI-datalink has a decryptor for Subaru.
Their website says, "Important note: this firmware doesn't override immobilizer. A second module with TB-SUB firmware is required for complete remote start solution." So, 2 modules are still required. One for transponder bypass, one for all the Can-features.
If I look at the 2008 Impreza on our website, we offer the TB-Subaru as transponder bypass (dealer tool required). Or, use one of the clients 3 keys (all subarus normally come with 3 keys).