I'd like to hold/press a single entry and have my activities list show a checkbox where I can select multiple entries.

Add a pulldown that allows me to delete and share the selected entries.

Finally, it would be really cool if I could select multiple entries and graph/summarize them. I would like to be able to share the summarized charts/graphs.

Another cool feature would be to be able to print a daily or summarized graph/chart.

Maybe you could limit summarization to a single week or month. if so, allow the user to specify which day begins the week.