With BuyMonero.net, you get your own bot that will place a daily buy order for an amount of XMR that you specify. If no one sells to the bot in 24 hours, your bot will make a second buy order that is sure to be filled. There is a small fee for the service - currently 1% (so 1 XMR lets you buy 100 XMR on the exchange).
You guys are reading my mind. Last few days I thought a lot of such a service for those who don't have trading bots. Based on my observations of my trading bot, each new bot competing with the other bots on Poloniex in order to buy have a big impact on the buy pressure. This is a great service - just don't make your bot better and faster then mine
What do you use?