There are Voltimeter and Amperimeter in Meters section.

Since SimulIDE 0.1.6 Meters have an output to get the reading as voltage.

This value is updated at 50 Hz wallclock time no matter simulation speed.
If you want plot  fast changes you can set the simulation speed accordingly.

This can be useful in some cases. THis is an example, using Amperimeter output to plot transistor characteristic curves: