Xperia T
A few weeks after announcing the upgrade schedule for particular Xperia smartphones, Sony has released an alpha version of their Jelly Bean custom ROM. The move comes after the company received a small number of requests from Android devs so the latter can make early evaluation and testing of the software.

Being in alpha stage, this build is obviously for advanced developers only.  Regular  Xperia owners may want to avoid flashing the ROM since many everyday uses are nonfunctional. For instance, any inserted SIM cards are not recognized, radio connectivity (Wi-Fi, Bluetooth, NFC, FM radio) is disabled, and the user interface look and feel is not final. Google apps are absent as well.

Other requirements in using the software include testing with an unlocked Sony Xperia T, agreeing to waive the phone warranty when unlocking the boot loader, and acknowledging that Sony holds no responsibility for any damage whatsoever that may happen. To top it all, should you decide to unlock your Xperia T, you will be no longer entitled to obtain the final version of the Jelly Bean upgrade when it releases.

If you’re nonetheless quite the daredevil, you can proceed to the source link for complete flashing instructions.