Mash Health is a digital public service that enables users to find UK healthcare providers. It uses the data.gov.uk API to access healthcare information for a variety of service types, including hospitals, GP surgeries, pharmacies, clinics and social care.
Mash Petitions is a digital public service that enables users to explore UK parliament petitions. It builds upon the governments' e-petitions platform, exposes more detailed information and combines it with other open public data to enable interesting analysis and insight.
As a part of my day job I create prototypes for services on GOV.UK. We use these as one of the ways to research and learn more about the needs users have of government. It's a very effective and fast paced way to get a lot of vital feedback throughout the service lifecycle and use it to iterate quickly and frequently.