About Handy Data Logger (free)
This app can act as a rainfall chart to use with your rain gauge. You can also use it to record other daily or monthly data values such as sales, body weight, temperature, etc. This free version only supports a single parameter, but the paid version allows you to set up a number of different parameters that you want to record, and then easily enter numeric values each day or month. You can also import data from and export data to comma delimited (CSV) text files.
Once you have recorded data, you can view it in tabular, calendar, or graphical form. Data can be viewed for a given month, year, or all years. The graph can display the data as a line or bar chart, and a linear trend line can optionally be shown over the top.
Note: When importing from a CSV file, the format should be the same as the files the app exports. There must be a single header line containing the field names, and the first 4 fields must be Year,Month,Day,Value (Where the Value field can have any name, such as Rainfall). Following this may be the optional Comment field.
The paid version of this app, "Handy Data Logger", is identical except that it has no ads and allows multiple parameters to be created.