Genuine Tech2's are made by Vetronix (part of Bosch) and cost around $3000 new
The $400 cheapies on ebay are Chinese clones and are hit and miss with quality.
Some people have no problems at all with the clones, but I've heard of others that have packed up after a week or 2
Many of the clones also seem to come with Holden export flash mem cards which are no good for Aussie VE's
A laptop with a PCMCIA slot and a bit of software can reprogram the cards to do Holden, Vauxhalls, Saabs, Chevs etc
I pulled apart an RFA module from a 2007 Omega on the weekend - it doesn't have a separate eeprom, just a m16c/1N Renesas MCU,
433 Mhz radio receiver chip and CAN bus transceiver. All the key remote and TPM settings are saved inside the MCU.
The new TPM calibration is a whole new o/s firmware for the MCU chip, and tis2web is the only practical way to reprogram it.
It's possible to directly program the TPM cal into the RFA without a tech2 or tis2web, but wayyyy too fiddly to do.