If I understood correctly your use case, what I would do it so plot property history using the QueryPropertyHistory service and run it every X seconds to update the chart. In other words:
1 - Add the time series chart to the mashup
2 - Add the QueryPropertyHistory service from the Thing that has this historical data (for that you need a Value Stream assigned to it). Check Mashup loaded checkbox
3 - Bind the AllData from the Service to the Chart
4 - Configure the chart according to your scenario
5 - Add a refresh widget to the mashup
6 - Bind the Refresh Widget to the QueryPropertyHistory service.
Calling the service from time to time is the only way I know how to achieve your scenario.