If you are an hourly employee, do you charge your company overtime if you have to be on call?

For example, last Friday I had to log in from home and do about 15 minutes of work spread between 8-12pm. But it meant I couldn't leave the house because I had to keep checking for emails so I could do this one thing. Normally my boss handles it but she was out of town.

I happened to be watching TV so I didn't mind too much, but at the same time I feel like I should charge them something since I wasn't free. What do you think would be fair?