greatghoul/manifest.json

## manifest.json
{
  "name": "Detect if an extension installed",
  "description": "Detect if an extension installed",
  "version": "0.1",
  "manifest_version": 2,
  "permissions": [
    "management"
  ],
  "browser_action": {
    "default_popup": "popup.html"
  }
}

## popup.html
<body style="width: 400px; height: 150px;">
  <div id="output"></div>
  <script type="text/javascript" src="popup.js"></script>
</body>

## popup.js
var extensionIds = [
  ["Session Buddy", "edacconmaakjimmfgnblocblbcdcpbko"],
  ["Readability", "oknpjjbmpnndlpmnhmekjpocelpnlfdi"]
];

extensionIds.forEach(function(extension) {
  var output = document.getElementById('output');
  chrome.management.get(extension[1], function(result) {
    var extensionElement = document.createElement('div');

    console.log(result);

    if (result) {
      extensionElement.innerHTML = ""
        + "<h3>" + result.name + " (" + result.id + ")</h3>"
        + "<p>" + result.description + "</p>";
    } else {
      extensionElement.innerHTML = ""
        + "<h3>" + extension[0] + " (" + extension[1] + ")</h3>"
        + "<p style=\"color: red;\">Not installed</p>";
    }

    output.appendChild(extensionElement);
  });
});
	{
	"name": "Detect if an extension installed",
	"description": "Detect if an extension installed",
	"version": "0.1",
	"manifest_version": 2,
	"permissions": [
	"management"
	],
	"browser_action": {
	"default_popup": "popup.html"
	}
	}