The Mobile Calculator is a gimmick: a simple, standard-issue 50-cent commodity calculator gussied up to look like a cellular telephone. The most advanced feature is a clock. Designed by Naoro Miyazaki, it's skinny, yellow-green and very pretty, as far as calculators go. It is, however, $28.
Now, here's what would be really fantastic. First, this as an actual cellphone: the only changes needed are a sim card slot, a condenser mic and a speaker. Yes, with the old-school LCD display. Second, a cellphone made to look like a cheap calculator; a credit-card style wallet calcphone would be fantastic, but in lieu of that, I'll take one that looks like an old Wang or HP scientific model.
Momastore Product Page [MoMA]
Mobile Calculator - looks like a phone? [Tech Digest]