Jim Cramer won't buy Apple (AAPL - Get Report)  at its current price unless the tech giant engages in some radical disruption like buying medical-device companies. 

"We did like it when it was at $140, $150 -- but what's happened is that it's just literally up 40 straight points [since then]," Cramer said during an exclusive video-conference call for members of his Action Alert PLUS club for investors.

Cramer, whose charitable trust already owns AAPL, recommended against putting new money into the stock despite recent upgrades or positive comments about the stock from Bank of America, Morgan Stanley and Cowen. "You'd [just] be chasing" the stock's ongoing run-up, the expert said.

But Cramer said it'd be a different story if Apple made a radical move like buying Tandem Diabetes Care  (TNDM - Get Report) and Dexcom (DXCM - Get Report) , which have upended diabetics treatment by teaming up to create a Web-friendly monitoring system for blood glucose. Cramer said Apple should buy Tandem and Dexcom, whose systems can display your blood-glucose levels on an Apple Watch or iPhone.

"I think that Tandem should be bought ... and they should merge that with Dexcom," the stockpicker said. "They could give the [monitoring] device away and charge $10 a month and it would be a fabulous revenue stream."

However, Cramer isn't sure Apple will consider such a strategy, as he believes the company is "surprisingly not opportunistic." The expert said he once sold Apple management that it should buy Netflix (NFLX - Get Report) when that stock was far below current levels, but "it wasn't in their DNA. This [might] not be in their DNA, either. ...They want to invent [things themselves]."

To hear a complete replay of Cramer's monthly video-conference call, click here for a free 14-day trial subscription of Action Alerts PLUS. The stockpicker also expanded on his thesis regarding Tandem Diabetes and Dexcom in a recent column for Real Money, our premium site for active traders.