Bower is for client side Javascript what npm is for the server side and reads a component.json file to recognize dependencies that should be fetched at deploy time so I'd be happy it heroku would run it at slug compilation time.
Unfortunately I can not invoke npm or bower from a heroku console or one-off command (heroku run "npm help") (heroku run bash -> npm help) as it's possible with ruby's rake. I've put npm and node (latest/x versions) in my package.json but in the engines section, not the dependencies.
I think this could be solved by customizing the node buildpack but I consider this a little too heavy task just for activating something so obvious.
You can also setup a postintall command, something like this in your package.json
"dependencies": {
"bower": "0.6.x"
},
"scripts": {
"postinstall": "./node_modules/bower/bin/bower install"
}
Then npm install will also install bower dependencies.
Pros : one command to rule them all.
Cons : you unnecessarily embed bower as a dependency.
You can use run like this:
heroku run npm install git://github.com/webjay/kaiseki
You should delcare dependences with NPM in package.json file
All you install from shell will be deleted on exit shell. You are in a cloned instance.