I've created an app for the Shopify app store (an ecommerce platform) that provides a customer stock notification service: http://backinstock.info.
The app has been live for about three months, and there has been a slow but steady trickle of registrations and conversions to paid plans. This is good, but now I need to crank it up. The potential market is quite niche, but much bigger than I have reached so far.
After a few attempts at Google Adwords and SEO the problem I keep coming back to is that few people seem to actively search for something like this app.
Customers who have installed the app generally love it. I think the problem is that if you are a successful and profitable online store you are busy selling things rather than googling 'increase shopify sales'.
How can I reach customers who are doing fine, but could be doing better?
Everyone wants to make more sales! Offer to only demo/present your product, not to sell. If your product is good, it will sell itself. Also use that time to do a problem/solution ranking/analysis when you talk with them. I.e. does your solution rank with the top problems/areas these customers are experiencing? Even if you have no interest with solving say another more pressing 'issue' they have at least you will know why it is ranked higher (or lower).