You should be able to get the same result with wmctrl and its -a or -R switch.
You'll still need to wait for the Chromium window to be rendered, but you won't have to close the xvkbd window afterwards.

slightly off-topic:
Combine this with a pocketable computer (some compute stick or a Zbox pico or a single-board computer) that is powered by a powerbank, and you should be able to offload any computing from the aged N900 to a relatively powerfull "server" at rather low costs in terms of money and mobility.
For testing, any laptop will do that doesn't die due to overheating when stored running in your backpack.

Im not sure about the optimal interface betweeen those two devices though.
The obvious choice would be wifi, but you might need that for communicating with the outside world. A 2nd wifi adapter might be necessary.
An alternative could be Bluetooth (PAN), but the N900 only supports BT 2.1, which severely limits the data rate to 2.1Mbit/s.