You will need the `phonegap` CLI tool installed globally to use `grunt-phonegap`.

```shell
npm install phonegap -g
```
You should also install whatever system dependencies are required by the platforms
you intend to target.

For help with that, see [Platform Guides](http://docs.phonegap.com/en/3.1.0/guide_platforms_index.md.html#Platform%20Guides) from the Phonegap documentation.