http://www.supras.com/~riemer/sonictech/techtom/
It's a reprogrammable ROM (program) board for Toyota ECUs. This particular one is for Supras (7M-GTE and 2JZ-GTE Inline 6 Turbos).
At the risk of getting a lot of negative flames I will flatly state I am NOT a fan of so-called "piggyback" ECUs. I don't care if you're talking about a Venom, Unichip, or even the TRD SC supplementary ECU -- they are all "band aids" trying to circumvent (second guess) what the stock ECU is doing. It would be far better to get the stock ECU to do what you want in the first place!
Replacing the stock ECU with a aftermarket unit (Haltec, FAST, etc.) would be another option but they also have drawbacks. Generally speaking, they lack the redundancy, FEM (failure effects management aka "Limp Home Mode") of the OEM ECUs, and durability testing of an OEM ECU (if the racecar dies you tow it home, if your street vehicle dies you can be stranded -- automakers go to a lot of trouble to prevent you from getting stranded due to an ECU failure). The aftermarket ECU will have to get interfaced with the OEM system and because of the various different implementations for distributorless ignition, idle control actuators, crank angle sensors, variable valve timing systems, and "drive-by-wire" throttle its likely that some of the OE systems will need to be changed or lost. You can all-but forget about emissions controls and compliance. Finally, you will be starting with a blank sheet of paper for fuel and ignition maps -- you won't have the benefit of starting with the factory maps that cost thousands of man-hours to develop (and likely need only minor tweaks).
No, I think the best option is reprogramming the stock ECU. We just need to find a way to do it. The Ford people with Ford's "EEC-IV" and "EEC-V" engine control systems have a really cool option (for supported vehicles and calibrations) -- "J3 Service Port" upgrades. The Ford ECUs have an "expansion port" on the side called the "J3 service port." It is essentially a PCI Bus (oversimplified) for the ECU and a way to "upgrade" the stock processor with a new program. Devices plugged into the J3 Port can read the stock program and replace it, on the fly, with a revised program. The ECU remains otherwise stock and fully functional. If you "switch off" or physically unplug the J3 Upgrade device, the ECU reverts to the stock program automatically as the internal program is never changed (unlike the flash upgrades for the newer GM/Dodge/Ford ECUs). Check these out, to find out what they can do:
http://www.tweecer.com/tellmore.htm
http://www.eec-tuner.com/products.htm
BTW, the reason I know about these is I've been researching them to use in my Jeep, which runs a '93 Ford EFI 460 (7.5L for you metric guys). I've run out of what engine mods I can make before the stock ECU programming gets in the way (about 345hp/475#ft -- yes, it can outrun my Tundra even though the Jeep weighs 5,800# and runs 40" tires with 4.56 gears!). The coolest solution I found is swapping to a 5.0 "A9M" or 5.8L "ZA0" (CobraR) Mustang EEC-IV ECU and MAF (mass air flow sensor). Then I can use one of the tuneable J3 Port modules to tweak it as much as I want (although supposedly the stock "ZA0" 5.8L CobraR ECU works pretty well with a modded 460). FYI, the reason I have to switch ECUs is because the 460's ECU "calibration" is not one currently supported by any of the tuneable J3 Port modules -- in other words no one has figured out what all the data in that particular ECU does and therefore there is no "template" for modifying it. Also, the 460's before '96-97 used "speed density" fuel-metering instead of using a MAF to directly measure the incoming airflow.
I would DIE for a similar upgrade for a Toyota (especially Tundra or V8 Lexus) ECU!