If you are comfortable with Verizon coverage you could switch to Straight Talk and get a lot more for the money, including 25MB of data for a fixed price/month. Many of the Verizon phones, including some smartphones w/ wifi, can be registered on this MVNO's service.

Something like the Env3 can probably sync w/ google calendar and only require the cheaper $9.95 data plan. I'd pop over to the verizon sub-forum @ howardforums.com for more specifics on this. Of course smartphones are going to handle this much better and likely have a slightly better interface. In this sense, changing to a provider which would give you the option of brining in your own wifi enabled phone but w/o the extra $$ seems reasonable.