This isn't an April Fool's story--researchers at the University of Florida have developed a microchip and antenna that fits inside a standard pill capsule.
When swallowed, the pill communicates with a small electronic device carried or worn by the patient. That device then communicates with a cell phone or laptop to let doctors or others monitoring "medication compliance" know the patient has taken their medication.
The University of Florida researchers had to develop an antenna that was biodegradable. The one they came up with uses lines of silver on the capsule. I found a picture of the miniature dipole antenna on the University's research web page.
The research is part of National Science Foundation project CAREER: Ultra Low Power Passive Microsystems for Medication Compliance Monitoring.
The research abstract lists goals including the need "[to] characterize voltage multipliers to determine fundamental tradeoffs in input voltage, leakage, reliability and efficiency for RF scavenging" and "[to] develop on-chip multi-resonant passive structures that will lead to amplifier integration and isolation."
There is no mention of the frequencies being used with these devices, but the small antenna size, even with the zigzag linear loading shown in picture, would appear to limit them to frequencies above 1 GHz.