Depends on what you mean by monitoring a stream of data, but for integers and floats, 'split' does this within user-set minimum/maximum limits. There's also maximum and minimum. You can also use 'if then' statements(although it will show up as a having a bad expression, type 'if then' in a new object then click help-file), and you can also set up your own network of '', '==', '' objects. For signals, there's the signal versions of the comparison ops('
There's an object called [lbyl] (look before you leap) that's available for download from the link below. It can be used to ignore values that jump too far unless they are repeated a certain number of times. You might find it useful.