Optoma TW610STi is one of the more impressive interactive short throw projectors available. Built around a 1280x800 DLP chip and using TI's approach to interactivity, it shares some strengths with other projectors that use TI's interactive technology. However it delivers enough extras to let it stand out from the pack.
TI's interactive approach offers two advantages. There's nothing to calibrate, and the pen only has to see the screen, rather than touch it, which means you can use any surface as a screen.
Beyond these basics, the TW610STi offers higher brightness than most interactive short throw projectors, with a 3100 lumen rating and measured at 95% of the claim, and it maintains an unusually high percentage of brightness in interactive mode. It delivers high quality data images, good quality video for a data projector, and surprisingly high quality audio for its light weight and portable size. It's also one of the few projectors that lets you turn on both interactivity and 3D at the same time.
As with any interactive projector, finally, the TW610STi is much less expensive than an equivalent non-interactive model plus an interactive whiteboard would be. That, along with its combination of features, makes it a more than attractive choice at $999 street.