Some GSM HTC EVO 3D devices have an auto HBOOT downgrade tool
IMPORTANT: If you're on Sprint, then this is not for you.
Developer Flashmaniac has released an HBOOT downgrade tool for Vodaphone and unbranded GSM HTC EVO 3Ds that allows, with two steps, users to downgrade the HBOOT to 1.49.0007. The reason to do this is for obtaining S-OFF afterward using tools like Revolutionary.io's exploit.
Unfortunately for those with newer HBOOTS, this is not a one-step root/S-OFF and HTCDev unlocking is still in your future. What it does mean, however, is that once you're downgraded, you'll be able to S-OFF so that you can flash radios without reverting back to stock, locking the device, and accepting the OTA. S-OFF also means you'll also be able to flash kernels from normal recovery mode.
Before you proceed, make sure you read the directions carefully. You'll need to make sure your phone is one of the supported models. Unfortunately I can't test this out myself because I don't have any GSM phones laying about, so please let us all know how it works.[xda-developers]