This app comes with a selected set of Stanford Large Movie Review Dataset (Andrew L. Maas et al., 2011) that you can search with keywords.
Since the original dataset is used for sentiment analysis, you can use this app to check how related adjectives are to review scores.
The search is powered by the iOS version of Apache Lucene. Because of that, you can perform complex boolean queries such as "great and movie". Word form differences, such as singular and plural nouns, are also taken care of by Lucene.