For those who are interested in our technology, we're built with Ruby on Rails on top of a Nginx server. We use GitHub as our code repository and EngineYard to deploy our code to Amazon Cloud. We also use Amazon S3 as an image cache, as well as SendGrid, and Amazon SES to send transactional emails.
In the backend, we use SOLR as our food and exercise search engine (it's why you get relevant results when you search for say "apple"). We use Redis as a key-value store to cache certain popular results, so you don't have to wait as long.
Our mobile app is a native iPhone app written in Objective C, and uses the REST API provided by our web server.
Our nutritional and food database is very structured, so we know what types of foods you're eating. As a result, we're able to give personalized, relevant, and actionable advice to you based on your diet and activities. We think this is an area that could use more improvement though.