An appropriate understanding of a machine's competences may be critical for safe use. Sharing measures of real-time function reliability could help users to adjust their reliance on machine capabilities. We designed a vibrotactile interface that communicates spatiotemporal information about surrounding events and further encodes a representation of spatial uncertainty. We evaluated this interface in a driving simulator experiment with varying levels of machine confidence linked to a simulated degradation of sensor signal quality and varying levels of human confidence induced through a degradation of visual feedback. A comparison between variants of the system indicated positive performance effects of providing uncertain information compared to a more conservative solution that only provided information above a specific confidence level. Subjective reports revealed a positive acceptance of uncertainty signaling in low-visibility conditions, comparable to acceptance ratings of a fully confident machine that accurately signaled the precise location of events.