Depending on your texting needs some companies may be better than others. Many CRM's are being sold with texting added to it. However, its been my experience (some may disagree) that blast text messaging isn't productive for car dealers. Its a quick way to get on customers do not call list. However, a one v one text conversation with a consumer from a dealer is a lot more attractive and proved to be productive. For that you will want a system that holds your people accountable and it will need to be monitored. For that service I suggest a previous employeer of mine Contact At Once. It's an amazing tool! So many ways to deploy it and it can be added to your mobile website. When the chat comes into the dealership it acts just like a chat. Dealer accepts the conversation and engages (no pun intended) into the text conversation. It's opt in opt out and can be initiated by the dealer. Replies can even happen from a sales persons cell phone but within the CAO application. VERY COOL!
I can recommend you to someone who can show you a demo. It's not very expensive and the feedback I heard before I left was amazing.