It's not a matter of aiming small or finding a safe niche. Build something good and don't be afraid to aim big with broad appeal -- as long as focus isn't scattered. The market for early adoption may start off small, but that's frequently the case.

Consider HD TVs and displays. Years back, it was the enthusiasts who were the early adopters. But I can assure you HD is no niche market and the companies behind them were not aiming small.