Sony had two demos, one of a game of tennis, the other cycling. The latter was the more obviously useful. A map with directions, speed and direction data are displayed dynamically as the demo rolls through. Although you do have to look quite far to the right and up to see the screen, the imagine was very sharp and clear in artificial light. Better than Google Glass, in my opinion.
In fact, I could see the combination of being able to attach to any frame and a big manufacturer brand being an attractive one. We don't know the pricing yet, which is a concern. At £200 it would be attractive. At £400 it's not.
But here's the rub, and the real problem with both this and Sony's other fitness and lifestyle IoT devices. You need an Experia phone to use the Attach. And let's be frank, who has one of those? Particularly in the apparent target market of cycling, golf and tennis enthusiasts.
That's right: no one.* iPhones only at the clubhouse, gents. So long as Sony persist with their dwarf locked ecosystem all of this technology is wasted. Which in the case of the Smarteyeglass Attach is a shame.
* this may not be factually correct :)