Who else is offering memberships???

I think you're on the right track with this. Hand out flyers, ask for referrals, tell your team to approach houses beside each job they are at. Prices aren't crazy and you are giving a needed service in most cases. I like the exclusive pricing angle in making it feel like a limited time thing. I would just focus in what is making you money for now and keep this as high priority for your team to be speaking to everyone about. Also really listen to what potential customers are saying, "too expensive" "don't need it every month" "I can do it myself". Take all that information in and adapt! You're on the right track.

We do, but we don't want to charge monthly because then the client will re-evaluate your price every single month. Collect the entire membership cost up front and you'll be much happier and the client will only re-evaluate the cost once per year. 

Love Adams suggestion. We have a service contract. We don't offer levels but I do like that. Our service contract is one offering and customer can pay annually or monthly. The majority pay annually. I dont have a ton of clients on this but I would like to know how people create a stand alone service with this or work it into their work flow. That has been our biggest challenge.