How do I use the "input data" field in a transaction?

I’m assuming this can be used to insert arbitrary data, ASCII, etc. Right?

How do I use it? I think the answer is eth.sendRawTransaction, however I can’t find any documentation on how to use this, aside from the way that ethereum does it. Looks fairly involved… I need to sign the txn manually?

Can anyone point me to a guide or provide an example?

BUMP

anyone know how to do this? I guess I could start experimenting…