Depending on complexity of the project, these forums are a good place to start (project section). Alternatively, you could create an instructable and post the link here and on Twitter, no doubt it will be retweeted if you include the pimoroni handle.
The guys also sometimes pick up fan-made stuff for inclusion in the Bilge Tank, and if you feel that the project has wide appeal it might be worth trying to get in touch regarding a feature in the learning portal, if you are up to make a detailed write up that includes all the hardware+software steps.