We had a client recently that needed to sell a hardware product with a service plan. This is something that should be fairly simple to accomplish with Ubercart and Recurring Payments. 

But our situation was a little different.  We had one hardware product, but we were setting up attributes on that product to handle the different service plans.  If you're not familiar with attributes, think of selling a t-shirt with a catchy slogan on it.  You may want to sell that same t-shirt in different colors, and certainly in different sizes.

The way we set it up for this client was to set the various service plans as attributes. But that didn't work with recurring payments, because the UC Recurring Payments code simply went into the product to check for the recurring payment amount.  It didn't go into the attributes of that product.

The compromise we made was to set each service plan up as a separate product.  The initial price would be the sum of the hardware price and the service plan price, and the recurring price would be the amount of the service plan.

Thanks to Angie Byron AKA Webchick for the documentation on recurring payments that made this solution possible.