You can use Lotus Notes from a cell phone.
The support for using Lotus Notes from a cell phone is getting better. "New IBM Software Brings Web 2.0 to Mobile Phones" is an announcement from IBM: "Lotus Expeditor software platform is extending desktop computing and Web 2.0 capabilities to mobile phones."
There's also a rumor that support is coming for iPhones. "Notes e-mail may come to the iPhone" (Computerworld) quotes an IBM spokesman as saying that IBM Lotus Notes developers will be working on a Notes e-mail application for iPhone 2.0.