Simulating -walletnotify option in Electrum

When run in daemon mode, bitcoind accepts a parameter -walletnotify=<cmd> which runs <cmd> whenever a wallet transaction changes due to sending/receiving.

Is there a similar feature in Electrum? If not, how can it be simulated?

The watch_wallet script seems to do something similar but only works on individual addresses, not whole wallets. In addition, it only prints a message.

An old question - by the time I saw it - but the Electrum daemon - assuming it is running on Linux of some type must be polled from an external source with software or a cron job.

see Checking/polling a balance of an address in Electrum via the command line/RPC