Cron for scheduling, with a simple script to do whatever you need, like this
require 'twitter'
require 'httparty'
response = HTTParty.get('https://api.bitcoinaverage.com/ticker/global/USD/')
price = response['last']
client = Twitter::REST::Client.new do |config|
config.consumer_key = "YOUR_CONSUMER_KEY"
config.consumer_secret = "YOUR_CONSUMER_SECRET"
config.access_token = "YOUR_ACCESS_TOKEN"
config.access_token_secret = "YOUR_ACCESS_SECRET"
end
client.update("Price - " + price)
That should tweet the price every time cron runs it.