Does this exist yet? It’s like the widgets that let you email your legislator, but instead it uses Skypeout, Gizmo Callout, or other service. You have reminder text about the bill number and the topic. You push the button to ring out to the congresscritter and talk to a staffer or leave a message. If the service was developed in a brandable fashion, it could be subsidized by EFF or the Sierra Club or the NRA or whoever.
For that matter, Congress needs VOIP service. A public office could setting up a voice presense handle and use it for inbound calls. Is anybody doing this yet?