I built 6 apps for another ecosystem (Shopify https://apps.shopify.com/partners/socialproof-it) and had very much the same experience as you. We did the low fidelity approach like you and also found that has diminishing returns as the app market matures. Once we started focusing on one app for Shopify https://apps.shopify.com/shopify-recurring-payments we found the returns quickly dwarfed what we made before. For it allowed us to be the best for thats all we did. I would recommend not focusing on two apps but just doing one really well. Doing multiple apps means your mediocre in different things takes all your energy to be the best. PS: Love the idea your going to focus on Apple Watch no one is the market leader/expert so great place to be.
