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InfluxDB
Power Real-Time Data Analytics at Scale. Get real-time insights from all types of time series data with InfluxDB. Ingest, query, and analyze billions of data points in real-time with unbounded cardinality.
Take a look at the Simple Mobile Tools. They are open source and can be downloaded via F-Droid. The have a dialer and a contact app. The color of the app can be customised in the settings as well if you don't like the orange color theme.
NOTE:
The number of mentions on this list indicates mentions on common posts plus user suggested alternatives.
Hence, a higher number means a more popular project.