We recently purchased a toolbox form factor battery powered wet/dry vacuum. It is made by Milwaukee, the same manufacturer of our drill which allows the two devices to share batteries and chargers.
Many tool manufacturers make something similar, as I have a very similar vacuum at home from Porter Cable, the brand of many of my battery operated tools. Aside from being cordless and sharing batteries the rectangle shape is better for storing it compared to the typical round / canister body models.
These certainly do not replace full size shop vacs, but are a great alternative to the ~2 gallon corded models that I have used in the past. The argument to be had is that the corded models provide more power and are much lower priced than battery powered, e.g. the corded craftsman be found online for ~$30 USD, while battery powered models from tool manufacturers range from $50 - $120.
What do you or your installers use?