Darren’s performance with Kermit the frog is part of the E! Entertainment Red Carpet pre-show, which is set to air live on both US coasts at 1:30 p.m. ET / 10:30 a.m. PT and is scheduled to run for four hours. (Timezone Converter)  

A more precise on-air time for Darren and Kermit is not yet known.

Possible livestreams for the show, though more will turn up closer to air:  

 |    Link 1    |    Link 2    |    Link 3    |    Link 4    |

E!Online will also have a livestream for the Red Carpet arrivals beginning at 5:15 p.m. ET / 2:15 PT.  (Link)  And here is a stream for the actual Oscar ceremony if anyone wants to watch that as well. (Link)