In a Wizard-of-Oz experiment we investigate to what degree automatic activity recognition could support the use of prioritized lists for nursing documentation on hand held mobile devices. The study involved 15 nurses, 60 patients records and over 250 documented processes at a geriatric care ward. Based on time effort, interaction complexity, error rate and subjective system perception our wizard of oz study shows that activity recognition is a key factor in the usability and acceptance of the system. We also study the impact of varying simulated activity recognition errors and demonstrate that error rates of up to 25% do not aversely affect the documentation process.