I'm not familiar with Throwing Scarabs, but it seems to me that 1,000 gp for an intelligent item is rather very little...
Resolving this issue certainly requires heavy DM intervention. I'd probably call that some of the time, some of the Scarabs will be willing to help your Neutral Good butt out - but not automatically, all the time. They'd need a good reason. Ego 2 only means YOU are not easily dominated by THEM. It doesn't mean they do your bidding all the time. Also, some of the time, some of the Scarabs are actually on the lookout - but not all the time. It would strain even a magical creature to be on constant alert.
Moreover, I'd never allow taking 10 on Spot or Listen checks to avoid an ambush or detect a trap or something like that. I'd rather take average rolls, which means that your Scarabs only have a three-quarter chance of making the DC 10 check to aid another.
[MENTION=28278]jefgorbach[/MENTION]: I really don't get this part: "Therefore guaranteeing he'd never be flanked and always able to accept their Take15 on Listen, Spot checks and/or roll his own skill, using the higher result."
First you argue that the Scarabs must make separate checks, then you argue the PC wearing them would never be flanked (which is technically true with a Rogue, but not for the reasons you seem to think), and could "take 15"? How, why, by what means, where, when, who, what? Nononono. Telepathy doesn't work this way.
All in all, going the Aid Another route quickly leads into theoretical optimization territory, such as in the infamous
Nanobots build. One should probably impose rational, severe limits on what's possible, or have the game collapse.