This extension provides a generic way for you to define different types of relationships between your products, by defining a RelationType for each type of relationship you'd like to maintain.
You can manage RelationTypes via the admin configuration menu, and you can maintain product relationships via Related Products tab on the edit product UI.
Warranty & Support Products
When you create a RelationType you can access that set of related products by referencing the relation_type name, see below for an example:
rt = RelationType.create(:name => "Accessories", :applies_to => "Product") => #<RelationType id: 4, name: "Accessories" ...> product = Product.last => #<Product id: 1060500592 ...> product.accessories => 
You can access all related products regardless of RelationType by:
product.relations => 
If you install the spree-automatic-coupons extension you can also specify a discount amount to be applied if a customer purchases both products. Note: In order for the coupon to be automatically applied, you must create a coupon of type: RelatedProductDiscount and leave the code value empty (blank codes are required for coupons to be automatically applied).