In the latest release of the phonegap package which the platform generates it has some changes here:
// The client calls mail, call en text links with the window name set
// to `_self`. This causes a new browser to be opened with the error
// `UNSUPPORTED_URL_SCHEME`. To circumvent this we are overriding the window.open
// so the window is set to `_system` which properly handles these schemes.
window.open = function(strUrl, strWindowName, strWindowFeatures, callbacks) {
if (/^(mailto:|sms:|tel:)/.test(strUrl)) {
cordova.InAppBrowser.open(strUrl, "_system", strWindowFeatures, callbacks)
} else {
cordova.InAppBrowser.open(strUrl, strWindowName, strWindowFeatures, callbacks);
}
};
so generate a new phonegap zip, build and try again