I have this app on my DroidX and use it a lot. It's good to have if you can't get on xbox live at work or if you need it on the go.
I use 1337pwn (free) and it works beautifully for me.
There are a couple of other android based Live apps, like "Xbox 360 Live". Personally I've used 1337pwn and found that it's been good enough. Gives live status updates, allows you to add/remove gamertags, check their status, see their gamerscore, play history, send messages, etc.
You do not need to put in your gamertag and password to use it.