From Thursday 12th of June Lidl is selling Speaking Blood Pressure Monitors for £19.99. The advertisement shows an upper arm cuff and states "With warning in case of possible cardiac arrhythmia." Batteries and storage pouch included.
These Thursday offers always have limited availability so if you want one then it would be best to visit a store on the first day .
I hope this is helpful - I don't have shares in Lidl, just a local store.