GPSIO is a still-experimental replacement for the Garmin Communicator plugin, built on open web standards and using GPSBabel to read GPS data. Supported browsers are Chrome and (soon) Firefox. Supported OSs are Mac, Windows and (soon) Linux.
To comply with browser security restrictions, GPSIO is composed of two parts: an extension and a host.
The host installer can be downloaded from http://gpsio.caltopo.com/gpsio-installer.zip. On windows systems you must unzip this file by right-clicking on it and choosing "Extract All"; the installer will not work properly if you navigate into the zipped folder by double- clicking on it in the windows file explorer. Either double-click on the install.py script or open up a command prompt and run "python installer.py".
The extension is installed through your browser.
GPSIO is free software (GPL) and is hosted at https://github.com/mtjacobs/gpsio. Contributions are welcome; two high priority items are Linux installation support and integration with non-Garmin GPSs (either through auto-detection or a user-selectable GPS type dropdown). Testing with additional GPS units is also valuable; send bug reports to info@caltopo.com.