I am working with a couple of people and we have created some software which, despite being a strong stand-alone, would be even better if integrated with another existing product. This has always kind of been our endgame.
So my question is, is it appropriate or even a smart idea to approach someone by whom you're hoping to get bought out, or let them find you when you're [potentially] more well-established?
This is quite the dilemma. If you approach the company, they are at a strategic advantage because they know you're interest and thus they can play you down. However, if you wait for the company to approach you, they may not notice or approach you.
That being said, you could do as Manny suggested in the comments and consider partnering with the company or licensing to them. Once you have something like that in order, it's possible that the company could approach you about an aquisition or you could bring it up. Either way, you'll have a stronger position to negotiate given your partnership or whatever you have worked out.
If you're set on having the company approach you, yet it seems as though they haven't noticed you, you could try:
hope this helps and best of luck!