This sounds like a promising idea. As someone who still reaches for a Smalltalk environment when I need to prototype something, ipython notebook is about the c

This sounds like a promising idea. As someone who still reaches for a Smalltalk environment when I need to prototype something, ipython notebook is about the closest thing I've ever found to the style of interaction you get with a Smalltalk REPL (aka "workspace"). Smalltalk deliberately blurs the lines between a text editor and REPL, and the debugger takes this a step further - a combined editor and REPL, within a suspended execution context. It could be argued, for example, that coding within the suspended context of a failed unit test, while the code underneath your cursor has this REPL-like liveness, is the non-cargo-cult way of doing TDD. I'm not trying to claim Smalltalk as the Greatest Thing Ever, but its existence (and its "otherness" - from the point of view of today's conventional style of development) are evidence that there are useful tools to be had, somewhere down a road less travelled.