The following uses for rubidium are gathered from a number of sources as well as from anecdotal comments. I'd be delighted to receive corrections as well as additional referenced uses (please use the feedback mechanism to add uses).
- rubidium is easily ionized, and so has possible use in "ion engines" for space vehicles (but caesium is somewhat more efficient)
- used as a "getter" in vacuum tubes
- photocell component
- used for making special glasses
- RbAg4I5 has the highest room temperature conductivity of any known ionic crystal. At ambient temperature, its conductivity is about the same as dilute sulphuric acid, suggesting uses in thin film batteries